Melt chocolate over a double boiler. Dissolve gelatin in cold water. If using gelatin sheets, immerse in cold water.
Cream sugar and egg yolks. Slowly pour the boiling milk over egg mixture. Pour in saucepan.
Stir with a wooden spoon over low heat until the mixture coats the back of the spoon.
Do not boil. Stir in the gelatin and melted chocolate. Strain into a bowl. Cool mixture.
Whip the heavy cream to a medium peak. Fold in the cool chocolate custard. Pour in a decorative mold. Refrigerate for 2 hours.
Unmold and serve with chocolate sauce around bavaroise.
Chocolate sauce:
combine cream and chocolate. Stir over low heat to melt. Cool