For Glaze: To melt chocolate, pour just enough boiling water over to cover. When soft to touch, carefully pour off water. Add Grand Marnier and 1 tablespoon of water. Combine well, remove pan from heat and add butter. Stir until smooth and shiny. Let cool.
For Mousse: Boil orange rind in water for 5 minutes. Drain. Place rind back in saucepan with sugar and 2 tablespoons water. Cook over medium high heat until crystallized. Remove from saucepan immediately. Soak cake in 1/4 cup Grand Marnier for 10 minutes, then squeeze between hands.
Melt chocolate in same manner as for glaze. Place chocolate over low heat and add egg yolks. Beat until well combined. Removed saucepan from heat and add butter gradually, beating until butter is incorporated. Add candied peel and fold in liqueur-soaked sponge cake.
Fold 1/3 of the beaten egg whites into chocolate mixture and combine the rest of the egg whites carefully. Pour into buttered mold and refrigerate for 4 hours. To unmold, dip outside of mold in hot water for a few seconds and then invert onto a dish. Coat with cooled glaze and serve chilled.