• Preheat the oven to 350F. Grease and flour a 9x13-inch baking pan.
• In a bowl of a stand mixer, whisk the butter with sugar until light and fluffy.
• Lower the speed of the mixer and add walnuts.
• Add flour spoon by spoon and mix. Set aside.
• In a different bowl, beat the egg whites until stiff.
• Fold them slowly into the batter, mixing gently with a spatula from underneath to the surface.
• Pour the batter into the prepared pan.
• Bake it at 350F for 30-40 mins or until golden brown. (if you bake it in a metal pan, the baking time is slightly shorter than in a glass pan)

While the cake is baking, prepare the glaze:

• In a bowl, mix the egg yolks and powdered sugar.
• When the cake is ready, remove it from the oven and pour the egg yolks mixture over the cake. Use a spatula to spread the mixture over the surface.
• Place the cake back into the oven and bake it for an additional 2-3 minutes. Then, turn off the oven and leave the cake inside for another 5 minutes to allow the glaze to harden.
• Wait until the cake completely cools down. Melt the dark chocolate in the microwave and drizzle over the cake.
• Slice the cake in squares using a very sharp serrated knife.