Preheat oven to 165C°. Line a slice tin with baking paper.
Roughly break the cream filled biscuits into smaller pieces.
Using an electric mixer beat the butter and sugars for 4 minutes or until light and fluffy. Add in the eggs and vanilla one egg at a time. Mix until combined, scraping down the sides after adding each egg.
Add flour and mix very gently until just combined.
Gently fold in white chocolate and filled biscoff biscuits.
Transfer to the lined slice tin. Smooth the top.
Add dollops of Biscoff spread over the top of the batter and spread over the surface. Top with the remaining plain biscuits.
Bake in oven for 30-35 minutes. The middle should be a little wobbly. If you find the brownie getting too brown before its cooked cover in foil to finish the cooking.
Cool in refrigerator and then slice into small squares.
