Pre-heat oven 180c/160c fan forced. Lightly grease a 30cm x 21 cm lamington pan, line base and sides with baking paper.
In a bowl, mix together flour, cocoa, brown sugar & peanuts. Add melted butter & mix well. Press mixture into pan.
In a medium saucepan, mix together sweetened condensed milk, smooth peanut butter, cream, extra butter & extra brown sugar, stir over a low heat until blended together. Set aside to cool for 5 mins. Whisk in egg & mix well. Pour over biscuit base. Bake for 15-20mins or until just set & golden. Cool completely.
Cut into 24 pieces & serve with an extra whole peanut on top.
If you like you can also add another layer on top of the caramel. Combine 225g melted chocolate & 50g copha, once caramel has cooled pour over evenly & refrigerate until set.