1 cup heavy cream
1 cup whole milk
2 ounces milk chocolate, coarsely chopped
2 ounces bittersweet chocolate, coarsely chopped
5 large egg yolks
1/3 cup sugar
1/4 teaspoon salt
2 teaspoons pure vanilla extract
Whipped cream, for serving (optional)
Preheat oven to 325 with a rack in lower third. Place eight 4-ounce pot de creme cups or ramekins in a medium roasting pan, and set aside.
In a medium saucepan, combine cream, milk, and chocolates over medium heat. Bring almost to a simmer and remove from heat. Let stand, stirring occasionally, until chocolate is melted and the mixture is smooth and combined.
In a medium bowl, whisk together the egg yolks, sugar, and salt. While whisking, add a little of the milk mixture to the egg mixture until combined. Add the remaining milk mixture, and whisk to combine. Whisk in vanilla. Strain through a fine sieve into a large liquid measuring cup.
Pour about 1/2 cup egg mixture into each pot de creme cup. Transfer roasting pan to oven; fill with enough boiling water to come halfway up the sides of the cups. Bake until custards are just set in the center, about 35 minutes.
Remove roasting pan from oven, being careful not to let the water spill over into the cups. Using tongs, transfer cups to a wire rack to cool completely. When cooled, cover with plastic wrap; chill in refrigerator at least 4 hours and up to overnight. Serve each topped with a dollop of whipped cream, if desired.
