For the cupcakes, preheat the oven to 180 °C and fill a muffin tray with paper cups.
Separate eggs and mix egg yolks with coffee, rum flavoring and 50 g sugar until well blended. Beat egg whites until stiff and mix with remaining sugar.
Mix flour, baking powder and salt well in a bowl. Slowly stir this flour-salt-baking powder mix into the egg yolk-coffee mixture. Fold in the beaten egg white.
Pour the batter into the ramekins and bake for about 20-25 minutes.
For the cream, mix the egg yolks with the sugar and beat until fluffy. Beat the egg whites until stiff. Stir the mascarpone into the egg mixture and fold in the beaten egg whites. Put in the fridge for about 1 hour!
Remove the cupcakes from the oven, soak in the liqueur (or sweetened coffee) and let cool on a wire rack.
Remove the cream from the refrigerator and decorate the cooled cupcakes with it.