Preheat oven to 180c/350f.
Grease and line a 20cm (8") square cake/baking tin with parchment paper and set aside.
Using a handheld mixer, cream together the butter and golden/raw caster sugar until light and fluffy.
75 g salted butter, 100 g golden/raw caster sugar
Whisk in eggs and vanilla and mix to combine, then add cookie butter and mix until incorporated.
2 eggs, 1 teaspoon vanilla extract, 300 g cookie butter
Now folding by hand, add plain/all-purpose flour and cocoa powder, and mix to combine.
120 g plain flour (all-purpose), 1 tablespoon cocoa powder
Fold in chocolate chips, then pour the brownie batter to the prepared tin. Scatter crushed biscuits on top of the brownie batter.
⅔ cup milk chocolate chips, 10 Lotus Biscoff biscuits
Bake for 30 to 35 minutes. Allow to cool before slicing.
Warm the extra cookie butter in the microwave, and drizzle over brownies (optional) to serve.