Ingredients
- Bottom Layer
- 6 tablespoons (3/4 stick) unsalted butter , cut into 6 pieces, plus extra for greasing pan
- 7 ounces bittersweet chocolate , chopped fine (Ghirardelli Bittersweet Chocolate Baking Bar)
- 3/4 teaspoon instant espresso powder
- 1 1/2 teaspoons vanilla extract
- 4 large eggs, separated
- Pinch table salt
- 1/3 cup packed light brown sugar
- Middle Layer
- 2 tablespoons Dutch-processed cocoa powder
- 5 tablespoons hot water
- 7 ounces bittersweet chocolate, chopped fine (Ghirardelli Bittersweet Chocolate Baking Bar)
- 1 1/2 cups cold heavy cream
- 1 tablespoon granulated sugar
- 1/8 teaspoon table salt
- Top Layer
- 3/4 teaspoon powdered gelatin
- 1 tablespoon water
- 6 ounces white chocolate chips (Valrhona discs)
- 1 1/2 cups cold heavy cream
- Block of Callebaut bittersweet chocolate (for making chocolate curls or shavings), optional
Preparation
Step 1
Bottom Layer
Preheat oven to 325 degrees. Butter bottom and sides of 9-inch springform pan. Melt butter and chocolate in medium bowl in microwave. (I originally melted the chocolate in a Pyrex measuring cup and then transferred it to a bowl. It's easier to just put it in a medium bowl to begin with.)
Stir in espresso powder. Cool slightly. Whisk in vanilla and egg yolks; set aside.
In stand mixer fitted with whisk attachment, beat egg whites and salt at medium speed until frothy, about 30 seconds. Add half of brown sugar and beat until combined, about 15 seconds. Add remaining brown sugar and beat at high speed until soft peaks form when whisk is lifted, about 1 minute longer, scraping down sides halfway through.
Using a whisk, fold one-third of beaten egg whites into chocolate mixture to lighten. Using a rubber spatula, fold in remaining egg whites until no white streaks remain. Pour batter into prepared springform pan, and smooth the top with a small offset spatula.
Bake until cake has risen, is firm around edges, and center has just set but is still soft (center of cake will spring back after pressing gently with finger), 13 to 18 minutes. (Watch closely. Mine was done at just 13 minutes. And don't doubt yourself. If the edges are firm and the cake springs back, it's done.)
Transfer cake to wire rack to cool completely, about 1 hour. (Cake will collapse as it cools. It's actually crazy how much it sinks!) Do not remove cake from pan.
Middle Layer
Combine cocoa powder and hot water in small bowl; set aside. Melt chocolate in medium bowl in microwave. Cool slightly.
In clean bowl of stand mixer fitted with whisk attachment, whip cream, granulated sugar, and salt at medium speed until mixture begins to thicken, about 30 seconds. Increase speed to high and whip until soft peaks form when whisk is lifted.
Whisk cocoa powder mixture into melted chocolate until smooth. Using whisk, fold one-third of whipped cream into chocolate mixture to lighten.
Using a rubber spatula, fold in remaining whipped cream until no white streaks remain.
Spoon mousse into springform pan over cooled cake and gently tap pan on counter three times to remove any large air bubbles; gently smooth top with offset spatula. Carefully clean any drips from the inside edges of the pan. Refrigerate cake at least 15 minutes while preparing top layer.
Top Layer
In small bowl, sprinkle gelatin over water; let stand at least 5 minutes.
Place white chocolate in medium bowl.
Bring ½ cup cream to simmer in small saucepan over medium-high heat. Remove from heat; add gelatin mixture and stir until fully dissolved. Pour cream mixture over white chocolate and whisk until chocolate is melted and mixture is smooth. Cool to room temperature, stirring occasionally, 5 to 8 minutes (mixture will thicken slightly).
In clean bowl of stand mixer fitted with whisk attachment, whip remaining cup cream at medium speed until it begins to thicken, about 30 seconds. Increase speed to high and whip until soft peaks form when whisk is lifted. Using a whisk, fold one-third of whipped cream into white chocolate mixture to lighten.
Using a rubber spatula, fold remaining whipped cream into white chocolate mixture until no white streaks remain. Spoon white chocolate mousse into pan over middle layer. Smooth top with offset spatula. Return cake to refrigerator and chill until set, at least 2½ hours. (I left it in the fridge overnight.)
To Serve
Take cake out of fridge 45 minutes before serving. Using the back of a paring knife, scrape along the edge of a block of chocolate to form chocolate shavings or curls.
Sprinkle these on top of the cake.
Run an offset between cake and side of springform pan; remove side of pan.
Clean and smooth the edges of the cake by running an offset around the cake.
Using a knife dipped in hot water, cut the cake into slices, Clean and rewarm the knife after each cut. Serve with a dollop of homemade whipped cream.