Press half of the sponge pieces into the bases of 4 x 1½ cup-capacity (375ml) glasses. Combine the coffee and liqueur and pour half over the sponge. Place the mascarpone, cream and icing sugar in a bowl and whisk until thick. Spoon half into the glasses. Repeat with remaining sponge, coffee mixture and mascarpone mixture. Refrigerate for at least 30 minutes. Sprinkle with chocolate to serve.