Preheat your oven to 325 degrees F. Spray three 8-inch pans with non-stick cooking spray, line the bottoms with parchment and spray again. Set aside.

Place the Biscoff cookies in a food processor or blender and pulse until the cookies are finely ground and resemble flour.

In a medium-size bowl, combine the Biscoff crumbs, all-purpose flour, baking powder, baking soda, and salt. Whisk until the ingredients are well-blended. Set aside.

In the bowl of a stand mixer fitted the paddle attachment, beat the butter and both sugars on medium speed until light and fluffy. Add the eggs, one at a time, beating well after each addition. Continue to beat for about two minutes, until the mixture looks lighter in color and fluffier in texture.

With the mixer on low speed, add ⅓ of the dry ingredients and mix until combined. Slowly add half of the buttermilk and mix until incorporated. Continue alternating the flour and buttermilk until it has all been incorporated. Scrape down the sides of the bowl and slowly mix for another 20-30 seconds.

Divide the batter evenly among your pans and bake for about 30 to 35 minutes. Cool 10 minutes on a wire rack before inverting onto cooling racks to cool completely.

In a stand mixer fitted with a paddle attachment, beat the butter and Biscoff spread or cookie butter on medium speed until light and fluffy. Gradually add the powdered sugar and beat for 2-3 minutes.

In a microwave safe bowl, heat the cream and then pour it over the white chocolate to melt. Stir until the mixture is smooth and silky. If needed heat the mixture for another 20 to 30 seconds and stir until the chips are melted. Set aside.

In a stand mixer fitted with a paddle attachment, cream the butter on medium-high speed for about two minutes. Slowly add the white chocolate (which should still be warm) while mixing on medium-low speed. If your buttercream feels soft after it's all mixed, just refrigerate the buttercream to harden it just a bit.

With the mixer on low speed, slowly add the sifted powdered sugar until incorporated. Scrape down the sides of the bowl and continue to mix for another minute. Add the vanilla and increase the speed to medium-high and beat the frosting for five minutes, until light in color and texture.

Heat the cream in a microwave safe bowl for 60 seconds. Pour the cream over the white chocolate chips and let sit for five minutes. Stir until smooth. Cool slightly.

Level each cake layer with a knife or cake leveler. Place the first cake layer on a cake board and top with ½ or ⅓ (depending on if it's 8-inch or 6-inch cake layers) Cookie Butter Filling. Crumble two cookies into small pieces and press into the Cookie Butter Filling.

Repeat step two with the remaining cake layers. Place the final cake layer top-side down. Apply a thin crumb coat around the cake and chill for 10 minutes in the freezer to set. Finish frosting the cake with the white chocolate frosting. Chill for another 10 minutes and apply the drip.