Two-Day Chocolate Mousse Cake

By Sprig Originals ✓ · cooked up in Sprig

One fudgy baked chocolate layer, one silky set mousse, and a clean slice every time. The mousse is stabilized with a whisper of gelatin so it holds sharp edges straight out of the springform — no fussy tempering, no mirror glaze, no pastry-school nerves. Bake the cake on day one, pour the mousse and chill overnight, then slice and serve on day two with a cloud of whipped cream, just like the retro Italian-American classic served by the slice.

Ingredients

• 3/4 cup all-purpose flour
• 1/2 cup Dutch-process cocoa powder
• 3/4 cup granulated sugar
• 1/2 tsp baking soda
• 1/4 tsp baking powder
• 1/2 tsp fine salt
• 1 large egg, room temperature
• 1/3 cup buttermilk
• 1/3 cup neutral oil, such as canola
• 1 tsp vanilla extract
• 1/3 cup hot brewed coffee or hot water

• 1 1/2 tsp unflavored powdered gelatin
• 2 tbsp cold water
• 8 oz semisweet chocolate chips or chopped semisweet chocolate
• 1/2 cup whole milk
• 2 1/4 cups heavy cream, cold
• 3 tbsp granulated sugar
• 1/4 tsp fine salt
• 1 tsp vanilla extract

• 1 cup heavy cream, cold
• 2 tsp powdered sugar
• 1 tbsp cocoa powder, for dusting
• 1 oz semisweet chocolate, for shaving

• 1 8-inch springform pan (or 8-inch round pan lined with a parchment sling)

Instructions

1. DAY ONE — BAKE THE CAKE: Heat the oven to 350°F. Lightly grease an 8-inch springform pan and line the bottom with a parchment round. Cut a strip of parchment about 3 inches tall and long enough to wrap the inside wall, and press it against the greased sides — this collar is what gives you clean mousse edges later.
2. Whisk the flour, cocoa, sugar, baking soda, baking powder, and 1/2 tsp salt together in a large bowl, breaking up any cocoa lumps with your fingers.
3. In a second bowl, whisk the egg, buttermilk, oil, and vanilla until smooth. Pour into the dry ingredients and whisk just until no streaks of flour remain, then whisk in the hot coffee. The batter will be thin and glossy — that is correct.
4. Pour into the prepared pan and bake 22 to 26 minutes, until the center springs back and a toothpick comes out with only a moist crumb. Cool in the pan on a rack for 20 minutes, then press the layer gently with your palm to flatten any dome so the top is level. Cool completely, at least 1 hour. Leave the cake in the pan with the parchment collar in place.
5. MAKE THE MOUSSE: Sprinkle the gelatin over the 2 tablespoons cold water in a small bowl and let it bloom for 5 minutes, until it looks like thick applesauce.
6. Put the chocolate in a large heatproof bowl. Heat the milk, 3/4 cup of the heavy cream, the sugar, and 1/4 tsp salt in a small saucepan over medium heat until it steams and small bubbles ring the edge, about 3 minutes — do not boil. Off the heat, stir in the bloomed gelatin until fully dissolved.
7. Pour the hot cream mixture over the chocolate, wait 1 minute, then whisk from the center outward until completely smooth and glossy. Stir in the vanilla. Let this base cool to just barely warm (about 85 to 90°F, warm-to-neutral on your fingertip), 15 to 25 minutes. If it cools too far and stiffens, set the bowl over warm water for 30 seconds and whisk smooth.
8. Whip the remaining 1 1/2 cups cold cream to soft peaks — it should hold a floppy curl and still look satiny, not grainy. Whisk one-third of it into the chocolate base to loosen it, then fold in the rest in two additions with a flexible spatula, stopping the moment the streaks disappear.
9. Scrape the mousse over the cooled cake layer still in its pan and smooth the top with an offset spatula, working from the center out. Tap the pan on the counter twice to settle it. Cover loosely with plastic wrap so it does not touch the surface and refrigerate at least 8 hours or overnight.
10. DAY TWO — UNMOLD AND SLICE: Run a thin knife around the outside of the parchment collar if it is stuck, release the springform ring, and peel the collar away in one slow motion. Transfer the cake to a serving plate using a wide spatula.
11. Whip the finishing cream with the powdered sugar to soft peaks. Dust the mousse top lightly with cocoa through a fine sieve and shave the chocolate over the top with a vegetable peeler.
12. To slice cleanly, dip a long thin knife in hot water, wipe it dry, and cut straight down in one stroke — no sawing. Wipe and re-dip between every slice. Serve each wedge cold with a spoonful of whipped cream.
13. Keep leftovers covered in the refrigerator up to 4 days; the mousse stays sliceable the whole time.

Chef's tips

Nutrition (per serving, estimated)

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