Quick and easy, great little treat.
Put a tin of coconut milk in the fridge to chill for a couple of hours (it should turn into coconut cream).
Crush the oreos into fine crumb, mix with sugar and melted butter. Press into the base and up the sides of the loose-bottomed cake tin or whatever.
Melt the chocolate over a pan of simmering water. Once it's melted, take it off the heat and stir in 3 heaping tbsp of peanut butter. Then add 3 heaping tbsp of chilled coconut cream. Whip for a minute or two using a hand mixer. Pour the filling over the crust and leave in the fridge to set.