Step 1:
1) chop up the muffins and lay at the bottom of a dish Step 2:
2) chop up the mars bars and melt Step 3:
3) mix in the mars bars with the custard Step 4:
4) pour on top of the muffins Step 5:
5) leave to cool in the fridge Step 6:
6) spread on whipped cream Step 7:
7) sprinkle marshmallows onto the cream Step 8:
8) keep in the fridge until served