Preheat the oven to 180°c bake and line a 20-22cm square baking tin.
Cream the butter and sugar until light and fluffy, then beat in the vanilla.
Sift the flour, baking powder, salt and cocoa together and add to the creamed mixture. Add the peanuts and mix well.
Firmly press the mixture into the base of prepared tin and bake for 10-15 minutes or until baked. Remove from the oven.
While the base in baking, melt and mix together the caramel ingredients (minus the unsalted peanuts) and whisk until smooth.
Pour over baked base, sprinkle with 50g of peanuts and return to the oven for a further 25-30 minutes or until the top of the caramel has set and turned a warm golden colour. Remove from the oven and allow to cool completely.
When the slice has cooled, gently melt together the chocolate and butter for the topping. Cover the slice with chocolate and allow it to set in the fridge before cutting and serving. Enjoy!