Finely crush chocolate cream cookies in a food processor. Melt 75g of the butter and combine with crushed cookies. Press mixture into the base and sides of a 24cm loose-bottomed tart pan and chill for 30 minutes, or until firm.
Combine peanut butter and icing sugar in a bowl and spread into the tart base. My filling was quite firm and what I found easiest was putting chunks of the mixture on top of the crust and then very gently spreading it out with my fingers, smoothing out the top.
Place chocolate and remaining 100g butter in a clean bowl of a pan of simmering water (don’t let the bowl touch the water). Stir until melted, then cool slightly. Spread over the peanut butter layer. If you’d like a smooth top like mine, pour the chocolate over the peanut butter filling and gently lift and tilt the pan so the chocolate covers the entire tart – don’t use a knife or spoon to spread or you’ll end up with lines in the chocolate. Chill for 30 minutes, or until firm.
My tart stayed nice for around 3 days, stored in an air-tight container in the refrigerator. Bring to room temperature, if desired, before serving, but it tastes nice cold too!