Julia Child’s Chocolate Mousse Cake Recipe

Active Time:

45 mins

Total Time:

2 hrs 45 mins

Servings:

16 servings

Made with an egg custard and whipped cream and flavored with chocolate, rum, and coffee, this decadent cake is chocolaty perfection — and happens to be gluten-free, with a texture that hits somewhere between a flourless chocolate cake and a cheesecake. This cake is best served at room temperature or just barely warm, and is rich enough that smaller piece might be enough.

Frequently asked questions

What is a chocolate mousse cake?

Most chocolate mousse cakes are actually a traditional chocolate cake layered with chocolate mousse. Julia Child's version is a cake made with a chocolate mousse, which gets its delicate texture by beating eggs and cream until they are light and airy. The cake sinks as it cools after baking for a light but almost fudgy texture.

Notes from the Food & Wine Test Kitchen

After whipping the cream until it has doubled in volume, you want to be careful to make sure it doesn't deflate. To avoid deflating all that air you incorporated into the cream, start by folding 1/3 of the whipped cream into the chocolate mixture. This initial step lightens the batter, so when when fold in the rest of the whipped cream, it retains its airy texture.

This cake is at its most tender and delicious when eaten slightly warm; however, you may cook it even a day or two in advance and leave it in its pan (covered and refrigerated when cool). Place it in a 200°F oven for 20 minutes to warm gently. Loosen edges using a sharp knife if needed and unmold onto a serving platter. A kitchen torch can be used to gently warm bottom of pan further to help cake release, if needed.

Cook Mode (Keep screen awake)

Ingredients

1 tablespoon instant coffee
4 tablespoons hot water
4 tablespoons dark Jamaican rum
14 ounces semisweet baking chocolate, chopped
2 ounces unsweetened baking chocolate, chopped
6 large eggs
1/2 cup granulated sugar
1 cup heavy whipping cream, chilled
1 tablespoon pure vanilla extract
Confectioners' sugar and/or sweetened whipped cream for serving

Directions

Place oven rack in lower third of oven and preheat oven to 350°F. Butter a (preferably nonstick) 9-by-9-by-2-inch cake pan. Cut a square of parchment paper to fit bottom of pan; butter parchment and place in pan. Dust inside of pan with flour; tap out any excess. Choose a roasting pan large enough to hold the cake pan easily, fill with enough hot water to come halfway up the side of the cake pan and set in the oven.
Swirl coffee and hot water in a medium saucepan; add rum and add chocolate to pan. Bring 2 inches of water to a boil in a larger pan; remove pan from heat and set chocolate pan in it. Let chocolate melt while you continue with recipe.
Add eggs and sugar to a mixing bowl placed over hot water and stir for several minutes until eggs are slightly warm to the touch and sugar is dissolved. Beat eggs on high speed for 3 to 5 minutes, or until mixture has at least tripled in volume and forms a thick ribbon when it falls from a beater; eggs should be the consistency of lightly whipped cream.
Place a metal mixing bowl over a larger bowl of ice and water, add cream and beat with a hand-held mixer or a large balloon whisk, using an up-and-down circular motion to slowly whip in as much air as possible. Beat until cream has doubled in volume and holds its shape softly. Whip in vanilla.
Whisk melted chocolate mixture until smooth and silky. Scrape it into egg mixture, stirring rapidly with a rubber spatula. When chocolate is partially incorporated, fold in 1/3 of the whipped cream, deflating cream and egg mixture as little as possible, then fold in the remaining whipped cream.
Scrape batter into prepared cake pan; it will be about two-thirds filled. Spread into an even layer with a small offset spatula using as few strokes as possible. Set at once in pan of hot water in preheated oven. Bake until cake rises up at least 1/2 inch from top edge of pan and a skewer inserted into cake comes out mostly clean, about 1 hour. Turn off oven, leave door ajar and let cake sit for 30 minutes in its pan of water; cake will sink evenly this way.
Remove cake in its water bath from oven and let it sit for another 30 minutes, so that it will firm up before unmolding and serving. Cake will sink down as it cools to about its original volume.
Loosen edges using a sharp knife if needed. Unmold cake onto a serving platter and decorate with a sprinkling of confectioners' sugar or with whipped cream. If you like, pass sweetened, vanilla-flavored whipped cream with cake.

Note

This cake is at its most tender and delicious when eaten slightly warm; however, you may cook it even a day or two in advance and leave it in its pan (covered and refrigerated when cool). Place it in a 200°F oven for 20 minutes to warm gently. Loosen edges using a sharp knife if needed and unmold onto a serving platter. A kitchen torch can be used to gently warm bottom of pan further to help cake release, if needed.