I also think I should chill the chocolate mixture for a few hours before putting the whip cream on. I think that might help the spreading. Frosting white over chocolate can be nerve wracking if you don't want chocolate showing through.
Chocolate Ice Box Cake
2 bars German sweet chocolate (8 oz)
2 Tbs water
2 Tbs confectioner's sugar
2 1/2 pints whipping cream
Angel Food Cake
1. Melt chocolate, sugar, ans water in a double boiler. Beat in egg yolks.
2. Stiffly beat egg whites and fold into chocolate mixture. Let cool. If runny, put in freezer. Remove when thick enough to spread. (Best if it's cold, not just cool.)
3. When cool, add 1/2 pt stiffly beaten whipping cream.
4. Cut angel food cake in half horizontally. Cover the top of the bottom half and replace top half of cake. Cover top and sides with chocolate mixture. Cool in refrigerator.
5. Beat the remaining whipping cream until stiff. Cover cake. Refrigerate.