The most extraordinary moist three-layer Biscoff Cake made by preheating oven to 350°F greasing and lining three 8-inch pans whisking 2 1/2 cups cake flour 2 tsp baking powder 1/2 tsp baking soda 1/2 tsp salt and 1 tsp cinnamon beating 3/4 cup softened butter 3/4 cup Biscoff spread and 1 3/4 cups sugar medium-high 2 to 3 minutes light and fluffy adding 5 room temperature egg whites in 3 additions beating well after each adding vanilla combining 3/4 cup sour cream and 3/4 cup buttermilk on low alternating flour in 3 additions with sour cream mixture in 2 additions beginning and ending with flour folding in roughly crushed 12 to 14 Biscoff cookies dividing approximately 538g per pan baking 24 to 27 minutes until tops spring back and toothpick clean cooling 10 minutes then on racks then beating 1 cup room temperature butter and 1 cup Biscoff spread smooth adding 4 to 5 cups sifted powdered sugar cream vanilla and salt beating fluffy assembling three layers with Biscoff buttercream crumb coating freezing 20 minutes applying final frosting and drizzling melted Biscoff and garnishing with whole and crushed cookies. A completely extraordinary three-layer speculoos Biscoff cake recipe.