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

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

In a large bowl, cream butter and sugar until light and fluffy. Add eggs one at a time, mixing well. Stir in vanilla extract.

Alternately mix in flour mixture and milk into creamed butter mixture, starting and ending with flour. Mix until just combined.

Divide batter evenly among prepared pans. Bake 25–30 minutes until a toothpick comes out clean. Cool completely on wire racks.

For buttercream, beat softened butter, gradually add powdered sugar, then mix in Biscoff spread, heavy cream, and vanilla until fluffy.

Assemble cake: Spread buttercream between layers, frost top and sides, and garnish with crushed Biscoff cookies.

Chill for at least 30 minutes before slicing and serving.