01 - Place chopped dark chocolate in a heatproof bowl set over a saucepan of barely simmering water, creating a double boiler. Stir continuously until completely smooth and glossy. Remove from heat source and allow to cool to lukewarm temperature.
02 - In a pristine mixing bowl, beat egg whites with a pinch of salt using an electric mixer or whisk until soft peaks form. Gradually incorporate half the granulated sugar while continuing to beat until stiff, glossy peaks achieve stability.
03 - In a separate bowl, whisk egg yolks with remaining granulated sugar and vanilla extract. Beat vigorously until the mixture becomes noticeably pale, thick, and creamy in consistency.
04 - Gently fold the cooled melted chocolate into the egg yolk mixture using a rubber spatula. Continue folding until completely uniform and no streaks remain visible.
05 - In a chilled bowl, whip heavy cream using an electric mixer or whisk until soft peaks form. The cream should hold its shape but still appear slightly soft.
06 - Add the whipped cream to the chocolate-yolk mixture. Fold gently with a rubber spatula until just incorporated, maintaining as much air as possible in the mixture.
07 - Carefully fold one-third of the beaten egg whites into the chocolate base to lighten the texture. Gently fold in remaining egg whites until just combined. Avoid overmixing to preserve the airy structure.
08 - Divide the mousse evenly among serving glasses or bowls. Cover each container with plastic wrap and refrigerate for minimum 2 hours or until completely set and firm.
09 - Just before serving, toss halved strawberries with powdered sugar if desired. Arrange strawberries on top of each chilled mousse. Garnish with fresh mint leaves and chocolate shavings for presentation.