Biscoff Cake Layers:

1. Preheat oven to 350°F/175°C. Line four 7-inch or three 8-inch cake pans with parchment rounds and grease with non-stick baking spray. Set aside.
2. Mix together 3 cups all-purpose flour, 1 cup granulated sugar, 2 cups brown sugar, 2 1/2 tsp baking powder, 2 tsp cinnamon, and 1 tsp salt with a stand mixer (with a paddle or whisk attachment) or hand mixer until fully combined.
3. Mix 1 cup of unsalted butter into the dry ingredients on a low speed. Continue to mix until no large chunks of butter remain, and the mixture looks crumbly.
4. Pour in 1 cup of egg whites and mix on low until incorporated.
5. Next, mix in 1 1/2 cups buttermilk, 2 Tbsp of vegetable oil, and 2 tsp of vanilla extract and mix on a low speed until fully incorporated. Scrape down the sides of the bowl with a rubber spatula, then beat on a medium speed for 30 seconds to make sure everything is properly mixed together.
6. Divide the batter evenly between the prepared pans. I like to use a digital scale to make sure each pan has the same amount of batter so that each cake layer is the same height.
7. Bake for 33-35 minutes or until a toothpick comes out with a few moist crumbs. Rotate the pans halfway through to help them bake evenly.
8. Let the pans cool for 10 minutes, then run a small offset spatula around the perimeter of the pan to separate the cake from the pan.
9. Place cake layers into the freezer for 30 minutes to accelerate the cooling process. Once the layers are cooled, carefully flip the pans and remove the layers.
10. Use a serrated knife to level the tops right before you plan to assemble your cake, or you can wrap and freeze them if you’re making them in advance.
11. If you make these cake layers in advance and freeze them, let them thaw for about 20 minutes before making your cake. The cake layers should still be slightly cold to the touch, which will make it easier to assemble your cake.

Vanilla Buttercream Frosting:

1. While the cake layers bake and cool make the buttercream frosting.
2. Beat 3 cups of unsalted butter on a medium speed for 30 seconds with a paddle attachment, until smooth.
3. Mix in 1 Tbsp of vanilla extract and 1 1/2 tsp salt on a low speed.
4. Slowly add in 10 cups of powdered sugar, 1 cup at a time. Add 1/2 cup of cream halfway through to make the frosting easier to mix.
5. Continue to mix on low speed for a few minutes, until the desired consistency is reached.
6. If the frosting seems too thick, add in additional cream (1 Tbsp at a time). If the frosting is too thin, add more powdered sugar (a quarter of a cup at a time).
7. Scoop 2 cups of the vanilla frosting into a separate bowl to make the cookie butter frosting. Set aside.
8. Cover the remaining vanilla frosting with plastic wrap to prevent it from crusting, then set aside.

Cookie Butter Frosting:

1. Mix 1 cup of cookie butter and 1/4 cup of heavy cream into the reserved 2 cups of buttercream. Stir with a rubber spatula until the cookie butter is fully incorporated and the frosting is smooth.
2. Cover with plastic wrap and set aside.

Assembling This Biscoff Cake:

1. Build this cake on a greaseproof cake board or flat plate. Use a dab of frosting to help stick the first cake layer to the board.
2. Add an even layer of vanilla frosting on top of the cake layer, then chill the cake in the freezer for 5 minutes.
3. Spread a second layer of cookie butter frosting on top of the vanilla frosting. Drizzle 1/4 cup of warm cookie butter on top of the cookie butter frosting. Repeat with the remaining layers until all are stacked.
4. Spread a thin coat of frosting around the cake to fully cover the cake layers to help lock in any crumbs.
5. Smooth using a bench scraper, then chill the cake in the fridge (20 minutes) or freezer (5 minutes) until the frosting is firm to the touch.
6. Add a second, thicker layer of vanilla frosting around the cake and smooth using a bench scraper.
7. Carefully press the chopped-up Biscoff cookies around the cake. Press larger chunks of cookies around the base and smaller bits higher up to create a cookie gradient.
8. Pipe a border around the top of the cake with the remaining frosting using your favorite piping tip. Top with a final drizzle of warm cookie butter and enjoy!