Start by making the peanut butter filling. Use a fork to whisk together the peanut butter and hot water until combined and smooth.
For the chocolate pudding, mix together the flour, cocoa powder and sugar in a small, heatproof bowl.
Spoon in the oil with 6 tablespoons of cold water and stir until combined.
Spoon out 1 rounded tablespoon of the cake mixture and pour the peanut butter filling into the resultant hole.
Smooth over the removed cake mixture, covering any visible peanut butter.
Cook in an 850W microwave for 3 minutes, then allow to stand for 1 minute.
Serve hot.
