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

Whisk together flour, granulated sugar, both brown sugars, baking powder, cinnamon, and salt in a large bowl.

Add softened unsalted butter and mix until coarse crumbs form. Stir in egg whites, buttermilk, oil, and vanilla until smooth.

Divide batter among the prepared pans, smooth tops, and bake for 33-35 minutes.

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

Make vanilla buttercream by beating softened butter and gradually adding vanilla, salt, and powdered sugar. Mix in heavy cream until fluffy.

Mix cookie butter with some of the vanilla buttercream to create cookie butter frosting.

Layer the cake by spreading vanilla buttercream between layers and adding cookie butter frosting.

Decorate with remaining vanilla frosting and crushed Biscoff cookies, then chill for 30 minutes before serving.

Slice and serve with coffee or tea.