For the bittersweet chocolate mousse, first pour water into a bowl and sprinkle gelatin on top. Let stand.

In double boiler, melt chocolate together with 3.5 oz (100 g) heavy cream. Mix until smooth.

Heat gelatin in microwave, stir, and combine with chocolate mixture. Cool slightly.

Beat remaining cream in mixer. Gently fold chocolate into cream.

Line 4 2½-inch (6-cm) square pans with plastic wrap so that mousse won’t leak through the sides. Pour mousse into pans and freeze.

When fully frozen, release mousse from pans. Cut each square on the diagonal to form 2 equal triangles. Return to freezer until ready to assemble.

Repeat process for milk chocolate mousse and white chocolate mousse.

To create perfect chocolate triangles the same size as the mousse triangles, create a stencil from a clear plastic sheet.

Melt both chocolates in microwave. Mix well and pour onto a patterned silicon sheet.

Let stand for 2–3 minutes. Place stencil on hardened chocolate and cut carefully around it with a sharp knife. Repeat until you have 32 chocolate triangles.

To assemble, place a chocolate triangle on a flat surface.

Gently lay a triangle of bittersweet chocolate mousse on top, followed by another chocolate triangle, a triangle of milk chocolate mousse, another chocolate triangle, and a triangle of white chocolate mousse.

Top with one last triangle.

To prepare berry fruit sauce, melt jam in a small saucepan.

Add frozen berries and stir until heated through.

Drizzle a small amount of sauce over plate before serving. Garnish with mint leaves.