1. CREAM together the butter and sugar until light and fluffy. Add the egg and vanilla and beat well. Add the sifted flour and cocoa, the milk and the coffee mixture, and beat just to combine.
2. SPOON into 12 × 1/3 cup capacity patty paper lined muffin pans. Bake in a moderate oven 180°C for 20 minutes or until cooked when tested. Cool on a wire rack for 10 minutes before turning out of pan to cool completely. Store in an airtight container until required.
3. COMBINE the marshmallows, chocolate and extra milk in a saucepan and heat gently until melted and combined. Cool for at least 30 minutes then fold in cream. Chill for several hours or until firm enough to pipe. Spoon into a piping bag then pipe onto the top of each cake, then dust with cocoa. Allow the topping to firm a little prior to serving.