Preheat your oven to 180°C (350°F) and grease two round cake pans.
Crush the Biscoff cookies into fine crumbs and set aside.
In a large bowl, cream together the softened butter and sugar until light and fluffy.
Add the eggs one at a time, mixing well after each addition.
Stir in the vanilla extract and mix until combined.
In another bowl, whisk together the flour and baking powder.
Gradually add the dry ingredients to the butter mixture, alternating with the milk until smooth.
Fold in the crushed Biscoff cookies gently into the batter.
Divide the batter evenly between the prepared pans and smooth the tops.
Bake for 25-30 minutes, or until a toothpick inserted comes out clean.
Let the cakes cool in the pans for about 10 minutes, then transfer to a wire rack to cool completely.
Whip the heavy cream with powdered sugar until soft peaks form.
Once the cakes are cooled, layer them with whipped cream and remaining crushed cookies.