1. Preheat the oven to 350°F and grease and line two 8-inch round cake pans with parchment paper.

2. In a medium bowl, whisk together the flour, baking powder, and salt.

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

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

5. Add the dry ingredients in three additions, alternating with the buttermilk, and mix just until combined.

6. Divide the batter evenly between the prepared pans and smooth the tops.

7. Bake for 28 to 32 minutes, or until a toothpick inserted in the center comes out clean.

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

9. For the frosting, beat the butter until creamy, then mix in the Biscoff spread.

10. Add the powdered sugar gradually, then add heavy cream a little at a time until the frosting is smooth and spreadable.

11. Place one cake layer on a serving plate and spread a layer of frosting over the top. Sprinkle with crushed Biscoff cookies.

12. Add the second cake layer, then frost the top and sides of the cake.

13. Decorate with more crushed Biscoff cookies and whole Biscoff cookies before serving.