Make the sponge cake. Combine the egg and sugar in a bowl and heat over a double boiler while beating with a whisk. Once it is warm to the touch, remove from the double boiler and continue beating until thickened.
Sift the dry ingredients into the bowl and mix until no longer powdery. Line your cake mold with kitchen parchment paper, pour in the batter, and bake in an oven preheated to 180°C for 15 minutes.
Once cooled, slice horizontally into two pieces. Shave one of the slices down to 13 cm diameter.
Make the strawberry mousse. Soak the gelatin in cold water. Combine the strawberries, lemon juice, and sugar in a small pot and heat while mashing up the strawberries.
When it becomes like strawberry puree, turn off the heat, add the gelatin, and mix to dissolve. Beat the heavy cream until thick, then add the cooled strawberry puree and mix.
Line a 13 cm diameter cake mold with plastic wrap and pour in Step 5. Chill in the refrigerator to harden until ready to use.
Make the syrup. Simmer the syrup's water and sugar for a bit to dissolve the sugar. Once cooled, add liqueur to taste.
Make the chocolate mousse. Soak the gelatin in cold water. Bring the milk to a boil in a small pot. Turn off the heat and add the chopped chocolate. Mix with a spatula to dissolve.
You can also heat the milk in the microwave using a heatproof dish. Then, add the chocolate to melt. Finely chop the chocolate in this case.
Once the chocolate has melted, add the soaked gelatin and mix until evenly blended.
I used gelatin that requires 100 ml of water per 2.5 g of powder. Please adjust according to the type of gelatin you use.
Put the heavy cream in a bowl and beat until thickened (to the soft peaks stage). Combine the egg white and sugar in a separate bowl and beat until stiff peaks form.
Add a small amount of the heavy cream to Step 10 and mix well. Add the remaining heavy cream and egg whites and mix together until no lumps remain to make the chocolate mousse.
Assemble the cake. Line the cake mold with plastic wrap and place the larger sponge cake into it. Brush with the syrup, then top with half of the mousse.
Brush the syrup on the 13 cm sponge cake, then top the mousse with the cake with the syrup-side up.
Remove the hardened strawberry mousse from the refrigerator, remove from the pan, and place on top of the sponge cake. Lightly press down. Just so the sponge sinks into the chocolate mousse slightly.
Top with the remaining chocolate mousse and use a palette knife to smooth the top. Let chill in the refrigerator for a few hours to harden.
Make the glacage. Combine all the ingredients except for the gelatin in a small pot. Bring to a boil while stirring to dissolve the ingredients. (Bring it to about 103 degrees Celsius.)
Turn off the heat and let it cool for 1~2 minutes. Add the soaked gelatin and mix to dissolve. Strain, then let cool until slightly thickened. (It should be warm to the touch.)
Remove the circular cake mold from the mousse. If you wrap the cake mold with a moistened and wrung out towel heated in the microwave, it will slightly warm the sides of the cake mold and make it easier to remove.
Pour the glacage over the surface of the mousse to cover the top and sides. Transfer to the refrigerator and chill until the glacage hardens to finish.
For the side decoration: Heat 15 g of heavy cream until it begins to boil and add 20 g of chopped white chocolate. Dissolve the chocolate. Use a spoon to drizzle the chocolate sauce on top of the cake.
The black of the chocolate and the pink of the strawberry mousse makes it really cute. You can also use regular cocoa for the black cocoa.
It's also cute when made in small circular cake molds.
Story Behind this Recipe
I wrote this to remember how to make a light mousse that isn't overpowering. Adding strawberries makes it a great cake with a tart taste.
I used gelatin that took 100 ml of water to 2 g of gelatin. Using this kind, the strawberry mousse takes 1 g, chocolate mousse takes 3.2 g, and the glacage takes 2.8 g. I used a lot of gelatin in the glacage to make it no-fail. (So, there's probably going to be some leftover in the container.) You can use frozen or fresh strawberries.