01 - Melt the dark chocolate in a heatproof bowl set over a pan of gently simmering water (bain-marie). Stir until smooth, then remove from heat and let cool slightly.
02 - In a medium bowl, whisk the egg yolks with half the sugar (1.5 tbsp) until pale and creamy. Add the vanilla extract.
03 - Gently fold the melted chocolate into the egg yolk mixture until well combined.
04 - In another clean bowl, whip the heavy cream until it forms soft peaks. Set aside.
05 - In a separate bowl, beat the egg whites with a pinch of salt until soft peaks form. Gradually add the remaining sugar (1.5 tbsp) and continue beating until stiff, glossy peaks form.
06 - Fold the whipped cream gently into the chocolate mixture until just combined.
07 - Carefully fold in the beaten egg whites in three additions, being careful not to deflate the mixture.
08 - Spoon the mousse into serving glasses or bowls. Cover and chill in the refrigerator for at least 2 hours until set.
09 - Before serving, toss the strawberries with powdered sugar if desired. Top each mousse with fresh strawberries and garnish with mint leaves.