In a large bowl, beat the mascarpone and pouring cream with electric beaters for 2-4 minutes, until fluffy and light.
Line the base of a rectangular serving dish (20 x 28cm x 6cm deep) with baking paper, letting it hang over the two long sides (This will make it easier to remove and handle the finished dessert from the dish for serving).
Combine the coffee and marsala in a large shallow dish. Working one at a time, dip sponge fingers briefly into the coffee mixture and lay them over the entire base of the serving dish.
Spread one third of the cream mixture on top in a smooth layer, and sprinkle with half the crushed gingernut biscuits.
Dip the remaining sponge fingers in the coffee mixture and make another layer on top of the cream mixture. Top with half the remaining cream mixture, and sprinkle with remaining gingernut biscuits. Dip the remaining sponge fingers in the coffee mixture and lay the final layer over the crushed biscuits. Top with the remaining cream mixture. Smooth the surface, and dust generously with cocoa powder.
Cover with cling wrap and chill in the fridge for at least 2 hours before serving. Use the overhanging paper to lift dessert out of the dish and cut into portions to serve.
Mix 3-4 teaspoons instant coffee in 1 cup (250ml) hot water.You can layer this dessert in individual dessert cups or mason jars and top with fresh cherries.