Cocoa (to dust) Whip cream with sugar until soft peaks form. Set aside. Beat the yolks with the remaining sugar and water. Cook carefully over low heat until thick and lemon-yellow. Continue beating over ice to cool, and add Grand Marnier. Fold this into the whipped cream. Beat the egg whites until stiff peaks form and fold them into the souffle mixture. Pipe into a buttered dish with a paper collar and freeze. Remove collar to serve and dust with cocoa.