CRUST: Combine wafers with melted butter.Add crushed Roca bar crumbs, blend well and turn into a 10-inch springform pan, patting crust well on bottom and up the sides about 1 inch.( not too thick at edge as it becomes hard to cut)

FILLING: Whip cream until stiffand set aside in fridg.Beat egg yolks until fluffy and thick (10 minutes),add icing sugar and Grand Marnier and continue to beat until well blended. Gently fold in whipped cream. Pour into prepared pan, freeze until solid, then wrap well for storage. Unmold onto serving platter at the last moment,decorate with thin orange slices; serve in thin wedges with a drizzle of warm chocolate sauce.

SAUCE: Melt chips and cream in a double boiler and beat until thoroughly blended. Stir in Grand Marnier and serve warm. This can be made ahead and refrigerated. Reheat gently before serving.