Prepare all ingredients at room temperature. Melt half of the dark chocolate using a double boiler.

Wrap the base of a 16cm mousse ring with 2-3 layers of aluminum foil to prevent water entry. Line the sides with silicone paper.

Heat the heavy cream until it starts to boil around the edges.

Pour the hot cream over the partially melted chocolate and let it sit for 1 minute.

Gently mix the chocolate and cream using a silicone spatula, focusing on the center to achieve a smooth ganache.

Whisk the eggs and sugar until pale and fluffy, about 5 minutes. The mixture should hold its shape for 3 seconds when lifted.

Slowly pour the ganache into the whipped egg mixture, folding gently to retain the air.

Pour the batter into the prepared mold, tap lightly to remove air bubbles, and place in a water bath.

Bake in a preheated oven at 160°C for about 1 hour. Turn off the oven and leave the cake inside to cool gradually.