Easiest Chocolate Mousse Cake

December 21, 2021
5 Stars
Photo by Julia Gartland. Prop Stylist: Anne Eastman. Food Stylist: Lauren Lapenna.
Author Notes

A dessert with several layers sounds complicated and time-consuming and therefore, no thank you. But here’s the deal: This one is none of those things. I remember enjoying chocolate mousse cake only at the end of special-occasion restaurant dinners with my parents in the ’80s (and yes, a puddle of raspberry coulis accompanied the slice). Teenage-me considered it the height of sophistication. And though it has since been replaced on dessert menus by trendier items, homemade chocolate mousse cake is timeless—a total showstopper—and, in this case, easy-peasy, too.

Here’s how: The base is a chewy cocoa brownie, inspired by Alice Medrich, studded with hazelnuts for crunch. It takes minutes to assemble (and if you’ve never had a brownie made with only cocoa, wowza are you in for a treat). The airy mousse doesn’t need gelatin or whipped egg whites. Instead, it’s made from whipped cream and melted chocolate mixed with water. Writing about Hervé This’ just-chocolate-and-water chocolate mousse, Kristen Miglore explains: “As you whisk, microscopic bits of water get suspended in the fat, thickening it and making it seem creamier. Then still more air is whipped into it and the cooling chocolate crystallizes around the air bubbles to make a remarkably stable foam, aka mousse.”

As a nostalgic nod to the pooled coulis of my youth, raspberries are folded in. Let it be said that while I am not a fruit-and-chocolate person, the berries here are nothing short of fantastic, adding unexpected juiciness to every bite. And the final layer is simply vanilla-smooched whipped cream, a wonderful, dare I say perfect, contrast to all the chocolate.

Once assembled, the cake needs at least a couple hours to set up, so plan accordingly. If you’d like, you can even make the brownie one day, then the mousse and cream the next. —Jessie Sheehan

  • Prep time 2 hours 50 minutes
  • Cook time 40 minutes
  • Serves 8 to 10
  • Brownie
  • Nonstick spray or softened butter, for greasing
  • 3/4 cup (63 grams) Dutch-processed cocoa powder
  • 6 tablespoons (45 grams) all-purpose flour
  • 1/2 teaspoon Diamond Crystal kosher salt
  • 1/3 cup (47 grams) hazelnuts, toasted, skinned, and coarsely chopped
  • 1 1/3 cups (284 grams) light brown sugar
  • 1/2 cup (113 grams) unsalted butter, melted
  • 1 1/2 teaspoons vanilla extract
  • 2 large eggs
  • Chocolate Mousse
  • 1/3 cup (76 grams) hot tap water
  • 3 tablespoons Dutch-processed cocoa powder
  • 8 ounces (227 grams) semisweet chocolate, chopped
  • 1 3/4 cups (397 grams) heavy cream
  • 1/4 teaspoon Diamond Crystal kosher salt
  • 1 teaspoon vanilla extract
  • 1 1/2 cups (180 grams) raspberries
  • Whipped Cream
  • 1 1/2 cups (341 grams) heavy cream
  • 1 1/2 teaspoons vanilla extract
  • 2 tablespoons confectioners’ sugar
  • Raspberries, for serving (optional)
  • Dutch-processed cocoa powder, for dusting (optional)
In This Recipe
  1. Make the brownie layer: Heat the oven to 325°F. Grease the bottom and sides of a 9-inch springform pan (at least 3 inches in height) with nonstick spray or softened butter. Line the bottom with a round of parchment paper and the sides with a long strip.
  2. In a small bowl, whisk the cocoa, flour, and salt. Whisk in the nuts.
  3. In a large bowl, vigorously whisk the brown sugar, melted butter, and vanilla. Whisk in the eggs. Fold in the dry ingredients with a flexible spatula, just until the last streak of flour disappears.
  4. Transfer the batter to the prepared pan and bake for about 35 minutes, rotating the pan at the halfway point. It’s ready when a cake tester comes out with a few moist, almost wet, crumbs that can be rolled into a ball between your fingers.
  5. Turn off the oven and let the brownie cool on a rack on the counter (or in the refrigerator, if you’re feeling impatient) until it’s room temperature. (At this point, you can also wrap the brownie and wait for up to 24 hours to proceed to the next step.)
  6. When the brownie is room temperature, make the mousse: Whisk the hot tap water and cocoa in a small bowl. In a large heatproof bowl set over a pot of simmering water, melt the chocolate (or use a microwave if you prefer).
  7. In the bowl of a stand mixer fitted with the whisk attachment, beat the cream, salt, and vanilla on medium-high speed until the cream thickens but does not hold peaks. When you lift the whisk, the cream should form ribbons as it falls and hits the surface.
  8. Stir the cocoa mixture into the chocolate with a flexible spatula. Gently fold in the cream until just a few streaks of cream remain (no need to clean this bowl—we’re using it again soon). Gently fold in the raspberries. Scrape the mousse into the pan and evenly spread it over the cooled brownie. Transfer to the refrigerator.
  9. Make the whipped cream: In the stand mixer bowl fitted with the whisk attachment, whisk the cream, vanilla, and sugar on medium-high speed until stiff peaks form. Spread the cream over the mousse layer and refrigerate for at least 2 hours and up to 24. If refrigerating overnight, very lightly cover the cake in plastic wrap.
  10. When ready to serve, remove the sides of the pan and peel away the parchment. Slide a long, thin knife between the bottom of the pan and the parchment covering the brownie bottom and release the cake, placing the cake on a serving plate, and carefully peeling away the paper as you do so.
  11. For the cleanest slices, dip a knife in warm water before cutting. Serve with more raspberries and cocoa if you’d like. The cake will keep lightly wrapped in the refrigerator for up to 3 days.

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Bio: Jessie Sheehan is a cookbook author, recipe developer, and baker. She is the author of The Vintage Baker (one of the Washington Post’s best cookbooks of 2018 and beloved by Oprah and Nigella) and the co-author of Icebox Cakes (both published by Chronicle Books). She has developed recipes for many cookbooks, besides her own, and has contributed recipes, written and/or created video content for Better Homes & Garden, Rachael Ray Everyday, the Washington Post, Fine Cooking, Yankee Magazine (October 2020) Epicurious, Food52, The Hallmark Channel’s Home & Family Show, The Feed Feed, The Kitchn, TASTE, Chowhound, Yummly, Spruce Eats and Little Sous, among others.

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