Grease a 15cm/6in microwaveable dish and line with cling film.
Add the butter and peanut butter to a microwavable bowl and cook for 30 seconds until melted.
Remove from the microwave and stir thoroughly. Leave to cool slightly then add the egg and stir in.
Sieve in the cocoa powder and flour then tip the sugar in. Mix until it forms a thick sticky paste. Tip into the microwavable dish.
Make holes in the top of the mixture and add the jam. Place in the microwave and cook for 15 minutes.
Remove and leave to cool. Cut into squares and enjoy.