Step 1 Preheat oven to 180C/160C fan forced. Grease a 20cm square slice pan and line with baking paper, extending 2 cm above the edge of the pan.
Step 2 Place cookies in the bowl of food processor and pulse until fine crumbs. Add melted butter and pulse until combined. spoon mixture into pan and press down firmly. Set aside.
Step 3 Place butter and chocolate in a medium saucepan. Stir until melted. Remove from heat. Quickly stir in egg, sugar, flour, cocoa powder and salt until just combined. Pour over cookie base. Sprinkle with peanuts.
Step 4 Bake for 40-45 minutes or until a skewer inserted in the centre comes out with moist crumbs clinging. Set aside to cool completely. Cut into 16 pieces.