Preheat your oven to 180°C (350°F) and grease a cake pan.
Crush the Biscoff cookies into fine crumbs.
In a bowl, cream together the 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 milk.
Sift together the flour, baking powder, and salt, then gradually add to the wet mixture.
Fold in the crushed Biscoff cookies until evenly combined.
Pour the batter into the prepared cake pan and smooth the top.
Bake for 30 minutes or until a toothpick comes out clean.
Let the cake cool before frosting with Biscoff spread.