Preheat oven to 350 deg F. Beat yolks and sugar until very light and fluffy. This will take several minutes even with an electric beater. The end product should have an off-white color. Add chestnuts and run to yolk-sugar mixture. Blend together and add half the almonds. Beat egg whites to stiff peaks and fold into mixture. Next, fold in rest of almonds and pour mixture into a buttered, floured, 10x2.5 inch spring mold. Place filled mold in oven. After 10 minutes, reduce heat to 325 deg F and bake for 35 to 50 minutes more, until cake has pulled away slightly from sides of mold. Remove from oven, let cool, unmold, and cut into two layers of equal thickness, leaving spring mold bottom attached to bottom of 1 layer. Apply chocolate whipped cream to top of bottom layer and arrange the other layer on top of that. Several hours before serving, glaze top of top layer with hot apricot glaze. When glaze has set, prepare icing. Balance cake in one hand, with hand under spring mold bottom, and dribble icing over top of cake. Tilt cake back and forth to coat evenly. Put cake on a rack and finish icing sides with a table knife or spatula. Refrigerate until icing sets. CHOCOLATE WHIPPED CREAM FILLING: Place chocolate and 3 tb water in a small pan, over low flame. Stir until chocolate melts into water and mixture is smooth. Start with 3 tb water and add more if necessary for smooth texture. Cool, but do not refrigerate. Combine with whipped cream. APRICOT GLAZE: Heat jam until it thickens slightly. Add rum off heat and apply immediately to cake. CHOCOLATE ICING: Soften chocolate in a double boiler over simmering water. Add butter to chocolate. When butter melts, stir it into chocolate until mixture is smooth and all lumps have disappeared. If icing is too thick to pour, add more butter. If it is too loose, add a small amount of chocolate. It should coat the spoon heavily and drip slowly off.