Place the biscuits into a bag and break into crumbs using a rolling pin
Heat the biscuit bits gently in a pan (add a couple of tablespoons of butter for a firmer base, optionally)
Press into the cake tins and chill in the fridge for half an hour
Combine the Custard and Marshmallows by gently heating in a pan
Top the biscuits bases
Sprinkle with Nutmeg if desired
Chill in the fridge for 2 hours
