Base:
Sift together flour, baking powder, and cocoa.
Add butter and vanilla essence and mix.
Press 3/4 of mixture into a sponge roll tin.
Put remaining mixture in the fridge.
Filling:
Melt butter, golden syrup, sugar, and condensed milk together.
Pour over the base. Sprinkle the remaining base mixture on top.
Bake for 30 minutes at 190°C.