This Chocolate Walnut Layer Cake with Rum is a celebration cake made with a light sponge, creamy chocolate walnut filling, rum-flavored syrup, chocolate ganache, and a coating of ground walnuts.
Chocolate, walnuts, and rum are one of those combinations that simply work. The cake looks elegant enough for birthdays and holidays, but none of the individual steps are particularly difficult.
The sponge is light rather than rich, which is important because there is plenty happening between the layers. The chocolate walnut cream, syrup, ganache, and walnuts bring richness without turning the whole cake into a heavy dessert.
Jump to:
- A Chocolate Walnut Cake Made for Celebrations
- Ingredients and Substitutions
- How To Make Chocolate Walnut Layer Cake
- Why the Rum Syrup Matters
- Tips for the Best Chocolate Walnut Cake
- Can I Make This Cake Ahead?
- How To Store Chocolate Walnut Cake
- A Chocolate Walnut Cake for Special Occasions
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- 📖 Recipe
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A Chocolate Walnut Cake Made for Celebrations
This isn't a heavy chocolate cake with walnuts stirred into the batter. Instead, it is a layered cake built around a very light sponge.
The sponge is brushed with rum-flavored simple syrup, then filled with a cooked chocolate cream enriched with butter and ground walnuts. A chocolate ganache covers the top, while whipped cream and walnuts finish the sides. So while the cake itself is light, the finished dessert has plenty of chocolate and walnut flavor.
It also has several different textures: soft sponge, creamy filling, silky ganache, and slightly crunchy walnuts. That balance is one of the things I like most about this cake.
Ingredients and Substitutions
You will find the exact quantities in the recipe card below. Here are the ingredients you need and the details that matter when choosing them.
For the Sponge Cake
- Eggs: Use large eggs, preferably at room temperature. The eggs provide most of the structure and volume in this light sponge cake.
- Granulated sugar: Sweetens the cake and helps the eggs whip into a thick, stable foam.
- All-purpose flour: Regular all-purpose flour is all you need. I have not tested this cake with gluten-free flour or other flour substitutes.
- Baking powder: Gives the sponge a little extra lift and makes the whole-egg method more reliable.
- Salt: A small amount balances the sweetness.
For the Chocolate Walnut Filling
- Whole milk: Whole milk gives the filling the best creamy texture. Two-percent milk should also work, but I would not use skim milk.
- Cornstarch: Thickens the chocolate pudding base. I don't recommend replacing it with flour because the texture will be different.
- Unsweetened cocoa powder: Use regular unsweetened cocoa powder. There is no need for sweetened cocoa or hot chocolate mix.
- Granulated sugar: Sweetens the cooked chocolate base.
- Unsalted butter: The butter turns the cooled chocolate pudding into a smooth, rich cake filling. It should be softened but not melted.
- Powdered sugar: Helps sweeten and smooth the butter before it is combined with the pudding.
- Rum extract or rum flavoring: This provides the characteristic rum flavor without requiring actual rum. Brands vary in strength, so adjust carefully.
- Ground walnuts: Grind the walnuts finely, but stop before they turn into walnut butter.
For the Rum Syrup
- Water and granulated sugar: These make a simple syrup that keeps the sponge moist.
- Rum extract: Add it after the syrup has cooled so the flavor remains noticeable.
You could use actual rum if that is what you prefer, but the cake does not require alcohol. I usually make it with rum flavoring.
For the Chocolate Ganache
- Milk chocolate: Adds sweetness and keeps the ganache from becoming too bitter.
- Dark chocolate: Balances the milk chocolate and gives the topping a deeper chocolate flavor.
- Heavy whipping cream: Melts with the chocolate to create a smooth ganache.
Using both milk and dark chocolate gives me the balance I want here. You can change the proportion slightly depending on how dark you like your chocolate, but I would not use milk chocolate alone because the topping can become overly sweet.
For Decorating
- Heavy whipping cream: Whipped cream creates the thin coating that holds the walnuts around the sides of the cake.
- Powdered sugar: Just enough to lightly sweeten and stabilize the whipped cream.
- Walnuts: Finely ground or finely chopped walnuts give the cake its traditional finish.
You do not need a thick layer of whipped cream. Think of it as edible glue for the walnuts rather than frosting.
How To Make Chocolate Walnut Layer Cake
There are several components, but the easiest way to approach this cake is to make them in order.
Step 1: Make the Chocolate Pudding Base
Whisk together the cornstarch, cocoa powder, and sugar in a saucepan. Gradually whisk in the cold milk until smooth, then cook over medium heat, stirring constantly, until the mixture thickens like pudding.
Cover the surface directly with plastic wrap and let it cool completely.
Do not combine warm pudding with butter. This is one of the most important details in the recipe.
Step 2: Bake the Sponge Cake
Beat the whole eggs and sugar with an electric mixer for about 7 to 10 minutes.
The mixture should become very pale, thick, and roughly triple in volume. When you lift the beaters, the mixture should fall back into the bowl in thick ribbons.
Whisk the flour, baking powder, and salt separately, then gently fold them into the egg mixture.
Bake the sponge in a prepared 9-inch springform pan at 350°F (180°C) for about 25 to 30 minutes.
Let it cool completely before slicing it horizontally into two layers.
Step 3: Finish the Chocolate Walnut Filling
Beat the softened butter with powdered sugar until creamy. Gradually beat in the completely cooled chocolate pudding, adding it a few spoonfuls at a time. Add the rum extract and ground walnuts.
The butter and pudding should ideally be close to the same temperature. This helps prevent the filling from separating.
Step 4: Make the Rum Syrup
Bring the water and sugar to a boil and simmer for about one minute, just until the sugar dissolves. Let the syrup cool, then stir in the rum extract.
Don't add the rum flavoring while the syrup is boiling. Adding it after cooling preserves more of the aroma.
Step 5: Fill the Cake
Place the bottom sponge layer inside the clean springform ring. Brush it evenly with about half of the rum syrup. Spread all of the chocolate walnut filling over the cake and level the surface.
Brush the cut side of the second cake layer with the remaining syrup, then place it over the filling. Refrigerate the cake for about 30 minutes so the filling can firm up.
Step 6: Make the Chocolate Ganache
Place the chopped milk and dark chocolate in a bowl. Heat the heavy cream until it is steaming and just beginning to simmer, then pour it over the chocolate.
Leave it alone for about two minutes before stirring until smooth and glossy.
Let the ganache cool slightly before pouring it over the chilled cake.
It should still flow easily but should not be piping hot, or it can soften the filling underneath.
Step 7: Decorate With Walnuts
Once the ganache has set, remove the springform ring. Whip the heavy cream with powdered sugar until firm peaks form.
Spread a thin layer around the sides of the cake and gently press the walnuts into the whipped cream.
Any leftover whipped cream can be used for a few rosettes on top, but that is completely optional.
Refrigerate the finished cake before serving.
Why the Rum Syrup Matters
Don't be tempted to skip the syrup. This sponge contains very little fat, so the syrup is what keeps the cake soft and moist after refrigeration. It also distributes the rum flavor through the cake instead of putting all of it in the filling.
Brush the syrup onto the layers rather than pouring it over them. You want moist cake, not soggy cake.
Tips for the Best Chocolate Walnut Cake
- Let the sponge cool completely before cutting it. Let the cooked chocolate mixture cool completely before adding it to the butter. And chill the filled cake before pouring the ganache over it.
- For the walnuts, grind them finely enough that they stick easily to the sides, but don't process them until they become powdery or oily.
- And don't rush the egg-beating stage. Even though the recipe contains baking powder, the air whipped into the eggs is still what gives this sponge its delicate texture.
Can I Make This Cake Ahead?
Yes, and I actually prefer it that way.
This chocolate walnut layer cake benefits from several hours in the refrigerator because the syrup has time to settle into the sponge and the filling becomes firm enough for clean slices.
You can comfortably make the cake the day before you plan to serve it.
Take it out of the refrigerator about 20 to 30 minutes before serving so the filling can soften slightly and the chocolate, walnut, and rum flavors are not refrigerator-cold.
How To Store Chocolate Walnut Cake
Keep the cake covered in the refrigerator for up to 3 to 4 days.
Because the filling and decoration contain dairy, don't leave the cake sitting at room temperature for extended periods.
For neat slices, use a sharp knife and wipe the blade clean between cuts.
A Chocolate Walnut Cake for Special Occasions
This is not an everyday one-bowl cake, but it also doesn't need to be intimidating.
The components are simple when you make them one at a time: sponge cake, chocolate walnut filling, rum syrup, ganache, and walnuts.
Together, they make a chocolate walnut layer cake that feels special enough for birthdays, Christmas, Easter, anniversaries, or any family celebration where a plain cake simply won't do. What about Halloween, for those of you out there who like playing with sugar paste?
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📖 Recipe
Walnut Chocolate Rum Cake
Ingredients
Cake Batter:
- 8 large eggs room temperature
- ½ cup granulated sugar
- ½ cup all-purpose flour
- 1 teaspoon baking powder
- ¼ teaspoon salt
Chocolate Walnut Filling:
- 2 cups whole milk
- 4 tablespoons cornstarch
- 2 tablespoons unsweetened cocoa powder
- 3 tablespoons granulated sugar
- 10½ tablespoons unsalted butter, softened
- 2 tablespoons powdered sugar
- 1 teaspoon rum extract
- ½ cup ground walnuts
Rum Syrup:
- ½ cup water
- 3 tablespoons granulated sugar
- 1 teaspoon rum extract
Chocolate Ganache:
- ⅔ cup milk chocolate chopped
- ⅓ cup dark chocolate chopped
- ½ cup heavy whipping cream
To Decorate The Cake:
- ¾ cup heavy whipping cream, cold
- 1 tablespoon powdered sugar
- 1 cup finely ground or finely chopped walnuts
Instructions
Make the chocolate walnut filling:
- In a medium saucepan, whisk together the cornstarch, cocoa powder, and granulated sugar.
- Gradually add the cold milk while whisking until smooth.
- Place over medium heat and cook, stirring constantly, until the mixture comes to a gentle boil and thickens to the consistency of pudding.
- Remove from the heat. Transfer to a bowl and press plastic wrap directly onto the surface to prevent a skin from forming. Let cool completely to room temperature.
- Beat the softened butter and powdered sugar for 2 to 3 minutes, until light and creamy.
- Add the cooled chocolate pudding to the butter mixture a few spoonfuls at a time, beating well after each addition.
- Mix in the rum extract and ground walnuts. Set aside until ready to assemble the cake.
- Important: The butter and pudding should be approximately the same temperature before combining them. If one is much colder than the other, the filling can separate.
Make The Cake:
- Preheat the oven to 350°F (180°C).
- Line the bottom of a 9-inch springform pan with parchment paper and lightly grease the pan.
- In a small bowl, whisk together the flour, baking powder, and salt.
- Place the whole eggs and granulated sugar in a large mixing bowl.
- Using an electric mixer, beat on high speed for about 7 to 10 minutes, until the mixture is very pale, thick, and approximately tripled in volume. When the beaters are lifted, the batter should fall back in thick ribbons.
- Sift the flour mixture over the eggs in two or three additions. Gently fold with a large spatula after each addition, taking care not to deflate the eggs.
- Pour the batter into the prepared pan and gently level the surface.
- Bake for 25 to 30 minutes, or until the top springs back lightly when touched and a toothpick inserted into the center comes out clean.
- Let the cake cool in the pan for about 10 minutes. Remove it from the pan and cool completely on a wire rack.
- Once completely cool, slice the cake horizontally into two even layers.
Make The Rum Syrup:
- Combine the water and sugar in a small saucepan.
- Bring to a boil and simmer for about 1 minute, just until the sugar has completely dissolved.
- Remove from the heat and cool completely.
- Stir in the rum extract after the syrup has cooled.
Assemble The Cake:
- Place the bottom cake layer inside the clean springform ring or on your serving platter.
- Brush approximately half of the rum syrup evenly over the cake.
- Spread all of the chocolate walnut filling over the cake in an even layer.
- Brush the cut side of the second cake layer with the remaining syrup.
- Place the second layer over the filling and press very gently to level the cake.
- Refrigerate for about 30 minutes to allow the filling to firm before adding the ganache.
Make The Chocolate Ganache:
- Place the chopped milk and dark chocolate in a heatproof bowl.
- Heat the heavy cream in a small saucepan until steaming and just beginning to simmer. Do not let it boil vigorously.
- Pour the hot cream over the chocolate and let stand for 2 minutes.
- Stir gently until the chocolate is completely melted and the ganache is smooth and glossy.
- Let the ganache cool for several minutes until it is still pourable but no longer hot.
- Pour over the top of the chilled cake and spread gently to the edges.
- Refrigerate for at least 1 hour, or until the cake and ganache are well chilled.
Decorate The Cake:
- Remove the springform ring and transfer the cake to a cake stand or serving platter if necessary.
- Beat the cold heavy whipping cream with the powdered sugar until firm peaks form.
- Spread a thin but complete layer of whipped cream around the sides only of the cake. This acts as the coating that holds the walnuts in place.
- Working over a baking sheet or wide bowl, gently press the walnuts onto the whipped-cream-covered sides of the cake. Rotate the cake as you work and reuse any walnuts that fall onto the tray.
- If desired, use any remaining whipped cream to pipe a few rosettes around the top of the cake.
- Refrigerate for at least 20 to 30 minutes before slicing.
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