1. Remove cake from pan. Remove parchment paper from bottom. Using a serrated knife, cut cake in half horizontally. Place bottom half of cake on a cake plate.
2. Spread evenly with the custard. (It may drip down the sides.) Top with remaining cake half. Refrigerate while preparing the glaze.
3. Heat the pareve whipping cream in a double boiler or a microwave (do not boil). Place broken chocolate pieces into the bowl and mix. Keep stirring until chocolate is melted and totally smooth.
4. When glaze is ready, quickly spread over top and sides of cake. Work quickly before it sets.