Line a 24-hole mini muffin tray with mini cupcake cases.
Make the mini cupcake sponges
Put the baking margarine and sugar into a large mixing bowl and beat together until fluffy.
Add the eggs and beat until fully combined.
Fold in the flour and cocoa.
Add the milk and fold through.
Fill the mini cupcake cases so that the batter is about 5mm (¼ inch) from the rim of each one.
Bake for 10-12 minutes until just springy on top. Cool on a wire rack.
Make the fudge frosting
Put the milk chocolate and dark chocolate in a heatproof bowl and melt in the microwave in 15-20 second bursts until just melted.
Whilst whisking the chocolate, gradually pour in the cream, whisking until thick and glossy.
Leave to cool for 30 minutes or until thick enough to pipe.
Transfer the frosting to a piping bag fitted with a closed star nozzle and pipe swirls on top of each cupcake. Allow to set for 30 minutes before serving.