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 sugars on medium speed until light and fluffy, about 2 to 3 minutes. The texture should be smooth and fluffy.
With the mixer on low speed, add the eggs, one at a time, beating well after each addition.
Scrape down the sides and bottom of the bowl. Turn the mixer to medium-high and beat the mixture for an additional 2 to 3 minutes. The texture should be smooth and the color light.
With the mixer on low speed, add 1/3 of the dry ingredients, followed by half of the buttermilk, another 1/3 of the dry ingredients, the second half of the buttermilk, and then the final 1/3 of the dry ingredients. Mix until the dry ingredients are 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.