Step 1

Preheat oven to 160C. Line eight 80ml (1/3-cup) muffin pans with paper cases. Place white chocolate and dark chocolate in separate heatproof bowls. Add milk, vanilla, 50g butter and 55g (1/4 cup) caster sugar to the white chocolate. Add water, coffee, and remaining butter and sugar to the dark chocolate. Stir each mixture over a saucepan of simmering water (make sure the bowl doesn't touch the water) until the chocolate melts and the mixture is smooth.

Step 2

Lightly whisk 1 egg in a bowl and add to the white chocolate mixture with half the plain flour and half the self-raising flour. Spoon among the prepared pans.

Step 3

Lightly whisk remaining egg in bowl and add to the dark chocolate mixture. Stir in cocoa powder and remaining plain and self-raising flour. Spoon over the white chocolate mixture in pans. Bake for 30 minutes or until crumbs cling to a skewer inserted into centres.

Step 4

Brush the Kahlua over the warm cupcakes. Cool in the pans.

Step 5

Use an electric beater to beat the mascarpone and icing sugar in a bowl until just smooth. Spoon into a piping bag fitted with a small nozzle. Pipe mascarpone mixture over cupcakes. Dust with cocoa powder.