[Jaconde Sponge: Preparation]
Put 1 egg white in a large bowl and let it sit in a fridge. Put 1 egg yolk in a small bowl and cover it with plastic wrap to prevent it from drying; set aside.
Use parchment paper to shape a mold of 24 × 17 × H2cm (9.4'' × 6.7'' × H0.8''); set aside.
Preheat an oven to 220℃ / 428 F.

[Jaconde Sponge]
Sift almond flour, powdered sugar, and cake flour into a large bowl.
Break an egg into the dry mixture, and use a whisk to mix until smooth.

Use an electric hand mixer to beat it on high speed for 5 minutes until whitish. Add the egg yolk, and beat it on high speed for another 5 minutes until smoother.

Remove the egg white from the fridge. (Wash the electric hand mixer, and wipe off well the water.) Beat the egg white on high speed until white and fluffy.
Add granulated sugar in 4 batches and beat at high speed each time.
Beat it until peaks form. The tip should hang down lightly.

Add the meringue to the flour-egg mixture in 3 batches, and fold it gently each time. (When it becomes marble, add the 2nd or 3rd meringue.)
Fold it until you don’t see any meringue left, then fold it another 10 times to make it a little smoother.

Put the cake batter in the prepared paper mold, and flatten it gently.
Lower the oven to 190 ℃ / 374 F and bake for 10 minutes. Remove from the oven, and transfer it to a rack to cool well.

Cut it into a rectangle of 20 × 7cm (7.9'' × 2.8''). The cut sponge should be smaller than the bottom of the half-round cylinder pan. Cover it lightly with plastic wrap to prevent it from drying; set aside.

[Chocolate Mousse]
Sprinkle gelatin over water and let it soak. To prevent unevenness, fill the container with water and gelatin in this order.
Use an electric hand mixer to beat heavy cream while cooling it in ice water until heavy and thick. Beat until the traces of the fall remain. Let it sit in a fridge.

Place the coarsely chopped chocolate in a bowl (aluminum or stainless steel bowl).
(I used small pieces of chocolate that not needed to be cut.)
Pour water into a small pot. The water shouldn't directly touch the bowl when you place the bowl with chocolate over the pot later. Bring the water to a boil until bubbling up, and turn off the heat. Put the bowl with chocolate over the pot so as not to touch the hot water directly.

Put milk and condensed milk in a small pot. Warm it for 1-2 minutes over medium-low heat while stirring. Turn off the heat, add the gelatin, and stir well to dissolve completely.
Remove from the heat, and cool down to 43℃ / 109 F or less, stirring it occasionally.

Transfer the chocolate to a large bowl. Add the milk, and stir well until smooth and glossy.
Cool down to 35℃ / 95 F (about body temperature) or less, stirring it occasionally.

Remove the whipped cream from the fridge and mix lightly to make it smooth. Add the cream to the chocolate in 3 batches, and fold it gently each time. (When it becomes marble, add the 2nd or 3rd meringue.) Fold it until smooth.

[Assembling]
Line the half-round cylinder cake pan with cake film. If you lightly brush the pan with liquor such as kirsch or brandy, you can line the film cleanly.
Put the mousse in the pan until 1 cm / 0.4'' lower than the height of the pan, and flatten it. Place the sponge on top and gently press into the mousse, and make the height of the sponge and mousse line up. Let it sit in a freezer overnight to harden.

[Next Day, Mirror Glaze]
Warm the side of the pan with a hot steamed towel, and slide a knife lightly between the cake film and the pan. Hold down the pan, and pull up the film to remove the mousse. Let it sit in the freezer again.

Make Mirror Glaze. Sprinkle gelatin over water and let it soak. To prevent unevenness, fill the container with water and gelatin in this order.
Put water, heavy cream, and granulated sugar in a small pot. Bring it to a boil while stirring sometimes. Remove from the heat, add gelatin and stir to melt.

Sift cocoa powder into the mixture, and use a whisk to stir well.
Transfer to an elongated container, and use a hand blender to blend for 1-2 minutes. (You can omit this blender process. If you use a blender, the mixture turns smoother.)

Strain it with a fine-mesh strainer and cool down to 25 ℃ / 77 F or below with ice water while stirring occasionally. It should turn heavy and thick a little.

Place the well-chilled mousse on a slightly smaller container (or on a rack). Pour the glaze over the mousse at once. Let it sit in a fridge for 3 hours to set.
Pipe the whipped cream, and top with strawberries and mint. It's all done!