Mix together all of the ingredients that will form the base and topping. The mixture should be slightly crumbly, but pack-down-able when you squeeze it between your fingers. Transfer 2/3 of the mixture into a lined 8x8 tin and pack it down evenly with your fingers or the back of a spoon. Pop the tin into the fridge while you get to melting the chocolate and peanut butter.
Add the chocolate and peanut butter into a microwaveable bowl and heat in 30 second intervals, until melted and fully combined. Remove the tin from the fridge and pour the melted chocolate onto the base layer, spreading it to the sides with the back of a spoon. Crumble over the remaining 1/3 of the base mixture. Return the tin to the fridge for 1 hour. Then, slice up, and ENJOY!