1. Preheat your oven to 350°F (175°C). Grease and line two 8-inch cake pans or three 6-inch pans with parchment paper.

2. In a medium bowl, whisk together flour, baking powder, baking soda, cinnamon, and salt. Set aside.

3. In a large bowl, cream together the butter, brown sugar, and granulated sugar until light and fluffy.

4. Beat in the eggs one at a time, mixing well after each. Add vanilla extract and Biscoff spread; mix until smooth.

5. Combine sour cream and milk in a small bowl. Alternate adding dry ingredients and milk mixture into the butter mixture, beginning and ending with dry. Mix until just combined.

6. Divide batter evenly into prepared pans and smooth the tops. Bake for 25–30 minutes or until a toothpick inserted comes out clean.

7. Let the cakes cool in the pans for 10 minutes, then transfer to a wire rack to cool completely.

8. For the buttercream, beat softened butter until creamy. Add Biscoff spread and beat again. Gradually mix in powdered sugar. Add heavy cream one tablespoon at a time until desired consistency is reached.

9. Assemble the cake by layering buttercream between each cooled layer. Frost the top and sides with remaining buttercream.

10. Decorate with swirls of frosting and crushed Biscoff cookies on top.