Base Grease a cake tin with a little butter. Melt the butter. Crunch the biscuits into crumbs. Stir in the biscuits and cocoa. Press the base into a layer on the bottom of a cake tin.
Cake again Wait until the mix is cool.
Add the vanilla essence and the flavouring. Whisk in the butter. Pour the cake mix onto the base. Place in the fridge. Resist temptation until the cake has fully set.