Preheat the oven to 200C/180C Fan/Gas 6. Line an 8 inch square baking tin.
Combine the melted butter, granulated sugar and light brown sugar in a large mixing bowl or the bowl of a stand mixer. Combine on high speed for 3-5 minutes.
Add the eggs and vanilla and combine again.
Fold in the flour, baking powder, white chocolate chunks and biscuits, using a wooden spoon/silicone spatula.
Pour the batter into the prepared tin, add a few extra biscuits for decoration and bake for 30 minutes, until golden on top. Let cool on a wire rack before slicing.
