Preheat your oven to 350°F (175°C). Grease and flour two 8-inch round cake pans, or line them with parchment paper circles and spray with non-stick cooking spray.

In a medium bowl, whisk together the all-purpose flour, granulated sugar, baking powder, and 0.25 tsp of salt. Set aside.

In a large bowl, using an electric mixer, cream together 0.5 cup room temperature unsalted butter until light and fluffy, about 2 minutes. Beat in the eggs one at a time, mixing well after each addition. Stir in 1 tsp vanilla extract and 0.25 cup Biscoff cookie butter until fully combined.

Gradually add the dry ingredients to the wet ingredients, alternating with the whole milk, beginning and ending with the dry ingredients. Mix until just combined, being careful not to overmix. Divide the batter evenly between the prepared cake pans. Bake for 25-28 minutes, or until a wooden skewer inserted into the center comes out clean. Let the cakes cool in the pans for 10 minutes before inverting them onto a wire rack to cool completely.

While the cakes cool, prepare the buttercream. In a large bowl, beat 1 cup room temperature unsalted butter with an electric mixer until light and fluffy, about 3-4 minutes. Gradually add the powdered sugar, one cup at a time, mixing on low speed until combined, then increasing to medium-high until smooth. Beat in 1 cup Biscoff cookie butter, 0.5 tsp vanilla extract, and the remaining 0.25 tsp salt. Add 2-3 tablespoons of heavy cream, one tablespoon at a time, until the buttercream reaches your desired consistency – it should be smooth and spreadable.

Once the cakes are completely cool, use a serrated knife to level the tops if needed. Place one cake layer on your serving plate or stand. Spread about 0.75 cup of Biscoff buttercream evenly over the top. Place the second cake layer on top and use the remaining buttercream to frost the top and sides of the entire cake. Finish by gently pressing the crushed Biscoff cookies around the base and/or on top of the cake.