Strips of orange zest (opt.) Whipped cream (for garnish) Note: Grand Marnier or Orange Curacao are suggested orange liqueurs. Wrap parchement paper or aluminum foil collars around six 2/3-cup souffle dishes and fasten with tape or string. In a small bowl, sprinkle the gelatin over the orange juice and set aside until softened. Place the bowl in a pan of hot water and stir occasionally until the gelatin dissolves, about 3 minutes. Set aside in the hot water. In a double boiler, beat the egg yolks and sugar over barely simmering water until the mixture is light-colored, creamy and warm to the touch, about 5 minutes. Remove from the heat and continue to beat until the mixture cools, thickens and forms a ribbon when the beater is lifted, about 3 minutes. Stir in the orange zest and liqueur. Scrape into a large bowl and set aside. Beat the cream until it is doubled in volume and forms soft peaks. Beat the egg whites until they form soft peaks. Stir the gelatin mixture into the beaten egg yolks. Place the bowl in a larger bowl half-filled with ice and water and stir with a rubber spatula until the mixture begins to thicken and mound, 2 to 4 minutes, depending on the type of bowl used (metal chills faster than glass or ceramic). Immediately remove from the ice water and fold in the whipped cream. About one-third at a time, fold in the egg whites until no streaks of white remain; do not overmix. Spoon 1/2 cup of the mousse mixture into each souffle dish and place a truffle in the center. Divide the remaining mousse amoung the dishes to bury the truffles. Smooth the tops, cover loosely with waxed paper and place on a tray in the refrigerator until set and chilled, about 2 1/2 hours. Before serving, remove the paper collars. Decorate the tops with whipped cream and strips of orange zest, if desired. Serve chilled.