01 - Place chopped dark chocolate in a heatproof bowl set over a saucepan of barely simmering water. Stir continuously until completely smooth and melted. Remove from heat source and allow to cool for 5 minutes.
02 - In a spotlessly clean bowl, beat egg whites with a pinch of salt using an electric mixer until soft peaks form. Gradually add half the granulated sugar while continuing to beat until stiff, glossy peaks form.
03 - In a separate bowl, whisk egg yolks with remaining granulated sugar and vanilla extract until mixture becomes pale yellow and creamy in texture, about 3-4 minutes.
04 - Gently fold cooled melted chocolate into the egg yolk mixture using a rubber spatula. Continue folding until completely incorporated and no streaks remain.
05 - In a chilled bowl, whip heavy cream with electric mixer until soft peaks form. Be careful not to overwhip—cream should still have movement.
06 - Gently fold whipped cream into the chocolate-yolk mixture using light, circular motions. Stop when just combined to maintain airy texture.
07 - Fold in one-third of beaten egg whites to lighten the base. Gently fold in remaining egg whites until just incorporated. Do not overmix or mousse will deflate.
08 - Divide mousse evenly among serving glasses or bowls. Cover with plastic wrap and refrigerate for minimum 2 hours or until completely set.
09 - Just before serving, toss strawberries with powdered sugar if desired. Arrange strawberries on top of each mousse portion. Garnish with fresh mint leaves and chocolate shavings.