To make an icebox pudding cake, cook a sweetened egg custard, add melted chocolate, spoon the filling into a baking dish lined with graham crackers, chill the cake for two to three hours, and top it with fresh whipped cream. This recipe yields eight servings.
Cut 3 tablespoons cold unsalted butter and 9 ounces bittersweet chocolate into small pieces, and set them aside. Put a saucepan over medium heat, and pour in 3 cups milk. Add 1 1/2 cups half-and-half, 1/2 teaspoon coarse salt and 1/2 cup plus 2 teaspoons white sugar. Stir thoroughly, and simmer the mixture.
While the milk mixture simmers, put 8 egg yolks into a mixing bowl. Whisk them, add 1/2 cup plus 2 tablespoons white sugar, and whisk again. Whisk in 1/3 cup unsweetened cocoa powder, 3/4 cup milk and 4 1/2 tablespoons cornstarch. Keep whisking while you slowly add the hot milk.
Cover the saucepan with a fine strainer, and carefully pour the custard back into it. Remove the strainer, and whisk the mixture until it boils. When the custard thickens into a pudding, take the pan off of the burner, and pour the contents into the bowl of an electric mixer. Attach the mixing paddle, and set the machine to medium. Add the chopped chocolate, and beat the custard until the chocolate melts.
After two or three minutes, pour in 1 tablespoon vanilla extract. Add the butter one piece at a time, and beat the custard until it is cool. This takes up to 10 minutes.
Line the bottom of an 8-inch baking dish with graham crackers, and cover them with 1/3 of the cooled custard. Repeat two more times. Refrigerate the pudding cake for two to three hours.
Shortly before serving time, put 3/4 cup heavy cream and 2 tablespoons confectioner's sugar into the bowl of an electric mixer. Attach the whisk, and whip the cream until it forms billowy peaks. Dollop the whipped cream over the pudding cake, and serve immediately.