4 large egg yolks
4 tablespoons sugar
2 cups heavy cream
8 ounces bittersweet chocolate, melted
1 teaspoon vanilla extract
In a medium saucepan, whisk together egg yolks, 2 tablespoons sugar, and 3/4 cup heavy cream. Cook over medium-low heat, stirring, until mixture coats back of spoon, 3 to 4 minutes (do not boil). Remove from heat; whisk in melted chocolate and vanilla. Strain into a bowl; chill until cool.
With an electric mixer, beat remaining 1 1/4 cups heavy cream with remaining 2 tablespoons sugar until stiff peaks form. Stir 1/3 of whipped cream into cooled custard mixture, then gently fold in the rest with a rubber spatula.
Spoon into serving dishes; chill, covered, at least 30 minutes and up to 3 days.
A little cognac and some vanilla extract can be added.
Recipe based on Martha Stewart's recipe.