Preheat your oven to 350°F (175°C) and grease and flour five 6-inch round cake pans or prepare three 8-inch pans and slice layers later. In a large bowl, whisk together the flour, sugar, baking powder, and salt.

In a separate bowl, cream together the softened butter and eggs until light and fluffy. Gradually add the milk and vanilla extract, mixing until just combined.

Slowly add the dry ingredients to the wet ingredients, mixing until a smooth batter forms. Divide the batter evenly among the prepared cake pans.

Bake for 20-25 minutes, or until a wooden skewer inserted into the center of a cake comes out clean. Let the cakes cool in the pans for 10 minutes before transferring them to a wire rack to cool completely.

In a large bowl, beat the softened butter until creamy. Gradually add the powdered sugar, Biscoff cookie butter, heavy cream, and vanilla extract. Beat until the buttercream is light and fluffy.

Once the cake layers are completely cool, level them with a serrated knife if needed. Place one cake layer on a serving plate and spread a generous amount of Biscoff buttercream on top.

Repeat with the remaining cake layers, stacking them evenly. Frost the entire cake with the remaining Biscoff buttercream, creating smooth sides and top.

Decorate the top of the cake with crushed Biscoff cookies.

Chill the cake for at least 30 minutes before slicing and serving. Enjoy your delicious 5-layer Biscoff cake!