Mix together the amaretti biscuits and melted butter and press into the base of a 18cm (7") spring-sided or loose-bottomed cake tin. Add the coffee and brandy to the hot water, stirring until dissolved. Place in a small shallow dish and allow to cool. Briefly dip the sponge fingers into the mixture, remove and leave to one side. Place the mascarpone and icing sugar in a bowl and mix together. Spread half the mascarpone mixture over the biscuit base. Lay the sponge fingers on top and finish with the rest of the mascarpone mixture. Chill the cheesecake for at least 30 minutes before serving, dusted with cocoa powder. NOTES : The ingredients from the classic Italian dessert, re-arranged into a tempting cheesecake. As an alternative to the sponge fingers try different fillings such as apricots, cherries, or one of the range of Bonne Maman compotes.