Butter or lightly spray with a non stick vegetable spray, an 8 x 8 inch (20 x 20 cm) square pan. Set aside.
Place the peanut butter, corn syrup, honey, cocoa powder, and light brown sugar in a large saucepan. Place over medium high heat and bring this mixture to a boil. Reduce the heat to low, add the marshmallows, and stir constantly until mixture is melted and smooth.
Remove from heat and stir in the vanilla extract, rice cereal, and peanuts. Press this mixture into the prepared pan and allow to set.
Topping: In a heatproof bowl over a saucepan of simmering water, melt the chocolate and butter. Spread over the squares and refrigerate until chocolate has set. Cut into squares with a sharp knife.