• Preheat the oven to 350°F. Line three 8-inch cake pans with parchment paper circles on the bottom. Spray with baking spray.
• In a large mixing bowl, beat the butter, cookie butter, and sugar for 2-3 minutes until combined. Add oil, egg whites, and vanilla. Beat again until creamy and smooth.
  1/2 cup salted butter, 1/2 cup (140g) cookie butter, 1 3/4 cup (350g) granulated sugar, 1/4 cup vegetable oil, 4 egg whites, 2 teaspoon pure vanilla extract
• Add half of the flour along with all of the baking powder, baking soda, and salt. Mix just until combined. Add half of the milk and sour cream. Mix again, stopping to scrape the bottom and sides of the bowl. Repeat with the remaining flour, milk, and sour cream.
  2 2/3 cups (317g) cake flour, 2 teaspoons baking powder, 1/2 teaspoon baking soda, 1/2 teaspoon salt, 3/4 cup whole milk, 3/4 cup sour cream
• Stir in the broken Biscoff cookies. Evenly divide the batter between the three prepared pans.
  14 Biscoff cookies
• Bake at 350°F for 23-28 minutes. Remove from oven and cool in the pans for 10 minutes before turning the cake layers out onto a wire rack to cool completely before assembly.

Frosting

• Make the frosting by beating the butter and cookie butter in a large mixing bowl until smooth. Add half of the powdered sugar and mix until combined. Add the remaining powdered sugar along with the cream and vanilla. Beat until light and fluffy, adding addition cream as needed to achieve a spreadable consistency.
  1 cups salted butter, 3/4 cup (210g) cookie butter, 4 cups powdered sugar, 1-2 Tablespoons heavy cream, 1 teaspoon pure vanilla extract

Assembly

• Place the first cake layer on a cake plate. Frost with about 3/4 cup of the cookie butter frosting. Heat 1/2 cup of the remaining cookie butter in the microwave for 30 seconds until pourable but not too hot. Drizzle about 1/4 cup of the melted cookie butter over the first cake layer. Repeat with the next cake layer, frosting, and melted cookie butter. Add the final cake layer and frost with a crumb coat of frosting. Transfer the entire cake to the freezer for 30 minutes to set the frosting before proceeding.
  3/4 cup (210g) cookie butter
• Once firm, using the remaining frosting to frost the top and sides of the cake. Heat the remaining 1/4 cup of cookie butter in the microwave for 20-25 seconds until pourable, then drizzle over the top of the cake. Use a spatula or spoon to nudge the cookie butter to the edges of the cake to create a drip effect, if desired. Sprinkle the remaining cookie crumbs around the top of the cake to finish.
  4-6 Biscoff cookies