Chocolate cake: 4 ounces (125 g) Valrhona 72% cacao Araguani dark chocolate, chopped 1 stick (125 g) unsalted butter 1/2 cup (110 g) superfine granulated sugar 2 large eggs (100 g) 1/3 cup (35 g) all-purpose flour, sifted Smooth chocolate cream: 2 1/2 ounces (70 g) Valrhona 72% cacao Araguani dark chocolate, chopped 7 tbsp (100 g) whole milk 7 tbsp (100 g) heavy cream 2 1/2 egg yolks (50 g) 1/4 cup (50 g) superfine granulated sugar Chocolate mousse: 6 ounces (170 g) Valrhona 72% cacao Araguani dark chocolate, chopped 1/3 cup (80 g) whole milk 1 egg yolk (20 g) 4 egg whites (120 g) 4 tsp (20 g) superfine granulated sugar Thin chocolate sheet: 3 1/2 ounces (100 g) Valrhona 72% cacao Araguani dark chocolate, chopped Chocolate sauce: 1 1/2 ounces (50 g) Valrhona 72% cacao Araguani dark chocolate, chopped 6 1/2 tbsp (95 g) still water 2 1/2 tbsp (35 g) superfine granulated sugar 3 tbsp (50 g) heavy cream Chocolate glaze: 3 1/2 ounces (100 g) Valrhona 72% cacao Araguani dark chocolate, chopped 1/3 cup (80 g) heavy cream 4 tsp (20 g) French butter 1/2 cup (100 g) Chocolate Sauce, recipe above For the chocolate cake: Preheat a convection oven to 340′F (170′C) or a regular oven to 350′F. Butter an 8-inch square mold (or a round one), 1 1/2 to 2 inches deep. Sprinkle it with flour.
Place the chopped chocolate in a bowl set over a saucepan of simmering water to melt. Remove from the bain-marie. Cut the butter into pieces and add it to the chocolate in the bowl, along with the sugar, eggs and sifted flour. Pour the batter into the prepared mold. Place it in the oven and bake for 20 minutes. The cake should look underdone. Unmold the cake on a rack and let cool. Clean, rinse, and dry the mold, then wrap it in plastic wrap. Place the cooled cake at the bottom of the mold.
For the smooth chocolate cream:
In a saucepan, bring the milk and cream to a boil. In a bowl, beat the egg yolks with the sugar. Off the heat, combine the two mixtures, then pour them back into a saucepan, and stir over gentle heat until the mixture reaches 185′F (85′C). Pour one-third of the mixture over the chopped chocolate, stirring well. Repeat two more times, stirring after each addition, then process the mixture with a handheld immersion blender (or whisk it vigorously). Pour the cream over the cooled cake. Refrigerate for 1 hour, then place in the freezer for 1 hour.
For the chocolate mousse:
Melt the chopped chocolate in a bowl set over a saucepan of simmering water. Remove the bowl from the bain-marie. In a saucepan, bring the milk to a boil. Pour the milk over the chocolate in the bowl, beating until the chocolate is smooth. Add the egg yolk and incorporate well. In the bowl of a stand mixer fitted with the wire whisk, beat the egg whites until stiff with a dash of the sugar, then, as the mixture begins to stiffen, add the remaining sugar. Incorporate one-third of the beaten egg whites into the chocolate mixture, then carefully fold in the remaining beaten egg whites.
Pour the chocolate mousse over the smooth chocolate cream in the mold. Smooth the surface with a spatula. Freeze for 2 hours.
For the thin chocolate sheet:
Melt the chopped chocolate in a bowl set over a saucepan of simmering water. Remove the bowl from the bain-marie and cool at room temperature until the chocolate thickens, then reheat it slightly for a few seconds in the bain marie until it reaches a temperature between 88′F and 90′F. Pour the chocolate over a sheet of acetate (or wax paper) and spread it out. Before it can set, cut out a square the same size as the cake. Place another acetate sheet on top and add a weight to prevent the chocolate from warping as it dries. Refrigerate for 2 hours.
For the chocolate sauce:
Place the chopped chocolate in a small saucepan and bring to a boil with the still mineral water, sugar, and cream. Stir continuously until the sauce is thick enough to coat a spatula.
For the chocolate glaze:
In a saucepan bring the cream to a boil, then remove it from the heat. Gradually beat in the chopped chocolate, beating it from the center outward. Set aside to cool to 140′F before adding the butter, then add the 1/2 cup (100g) of the chocolate sauce.
To finish the cake:
Remove the cake from the mold and discard the plastic wrap. Using a small ladle, pour the chocolate glaze (it should be warm, between 95′F and 105′F around the sides of the cake, then over the center. Using a cake spatula, evenly coat the sides and edges. Leave to set for a few minutes then transfer it to a cake plate. Remove the acetate from the thin chocolate sheet, and place it on the cake. Set the cake in the refrigerator to defrost for 2 hours before eating. Cut with a knife dipped in hot water for 30 seconds.