Makes enough for one 8 inch square tin
1 Preheat your oven to 170C/150C fan/Gas Mark 3. Stuff a ripped-off square of baking paper into an 8-inch square tin.
2 In a large bowl, beat the butter, peanut butter and sugar together until paste-like. There is no need to cream as you would for a cake.
3 Add the egg and vanilla and beat until combined. Again, there is no need to develop air.
4 Add the flour, peanuts and chopped chocolate, stirring gently to combine. Dollop the mixture into your cake tin and spread out to the edges, for it should be quite tough.
5 Bake in the oven for 25-30 minutes or until golden brown on top and moderately resistant when pressed. A skewer inserted should come out clean.
