Add sugar gradually and beat until stiff and well mixed. Grease two pieces of foil, place on large cookie sheet, divide egg white mixture in half on greased foil and spread into 10" circles. Bake at 250° F for 1 1/2 hours. Turn off oven and leave in until they have cooled. Beat whipping cream with a little sugar, Spread 1/3 of whipping cream over one egg white circle. Sprinkle chopped coffee crisp over the whipping cream. Next place second egg white circle on top. Ice sides and top of cake with remaining whipping cream. Garnish with shaved chocolate if desired. Chill in fridge for several hours until softened.