– 2 cups (500 g/17 oz.) mascarpone cheese – 1 cup heavy cream or 1 1/4 cups to stretch the mascarpone mixture – 1/2 cup (100 g/4 oz.) semi-sweet dark chocolate – 1 cup strong espresso – 3 to 4 tablespoons coffee liqueur such as Tia Maria or Kahlua – 30 sponge fingers or a 10" sponge cake – 1/4 cup caster sugar – 1/4 cup dark rum or Marsala – Garnish: chocolate shavings or powder