Crush biscuits
Melt butter
Add biscuits, mix well, press into flan dish
Melt chocolate, stir in coffee
Whip cream to soft peak
Put milk and marshmallows into pan
Stir continuously until marshmallows are melted
Remove from heat and stir in the melted chocolate, a little at a time
Using a balloon whisk, add cream
Pour over biscuit base and chill overnight
To serve sprinkle over grated chocolate or a crushed flake