In a bowl mix the mascarpone with the Marsala or sweet sherry to soften the mixture slightly. Add the sugar and then fold into the whipped cream.
Dip a sponge finger in the coffee mixture and then lay in the base of a 26 x 21 cm rectangular dish. Complete to cover the base of the dish and then spread over ½ of the cream mixture.
Dip more sponge fingers in the coffee and spread over the remaining creamy mixture.
Dust the top of the tiramisu with cocoa powder and sprinkle over the grated chocolate. Chill for 4 hours or overnight. Serve with strawberries.