In a medium bowl, using a hand electric mixer, cream butter with brown sugar together until light and fluffy.
Incorporate the eggs one by one.
Add vanilla.
In a different bowl, mix flour, baking soda, salt, and cinnamon.
Combine the mixture of flour with the mixture of butter.
Add the linseeds and mix well.
Cover a baking sheet with parchment paper and drop dough by rounded tablespoonfuls about 2 inches apart onto an ungreased cookie sheet.
Bake the cookies for about 15 minutes. Let them cool for 5 minutes on the baking sheet before removing them to a cooling rack.
The cookies will keep fresh for about two weeks in an airtight container.
Notes
Chill the Dough: If you find your cookies spread too much, try chilling the dough for 30 minutes before baking.
Room-Temperature Ingredients: Eggs and butter should be at room temperature for a smooth, even mix.
Watch the Oven: Oven temperatures can vary, so keep an eye on your cookies around the 12-minute mark. They should be golden around the edges but still soft in the middle.
Keep Fresh Cookies: Store in an airtight container at room temperature. They'll stay fresh for up to two weeks.
Freezing Dough: First, freeze dough balls on a sheet. Then, move them to a freezer bag. They're good for 3 months. When ready, bake straight from the freezer, just add an extra 1-2 minutes to your bake time.
Freezing Baked Cookies: Lay them out in a single layer in a freezer-safe container. They'll last for 3 months. To enjoy, thaw at room temperature or quickly warm them in the oven or microwave.