01 - Melt the dark chocolate in a heatproof bowl over a pan of simmering water (double boiler), stirring until smooth. Remove from heat and let cool slightly.
02 - In a clean bowl, whisk the egg whites with a pinch of salt until soft peaks form. Gradually add the granulated sugar and whisk to stiff peaks.
03 - In another bowl, lightly beat the egg yolks. Slowly add the cooled melted chocolate to the yolks, mixing until well combined.
04 - Gently fold the whipped egg whites into the chocolate mixture in three additions, being careful not to deflate the mixture.
05 - In a separate bowl, whip the heavy cream until soft peaks form. Gently fold the whipped cream into the chocolate mixture until fully incorporated and smooth.
06 - Spoon the mousse evenly into serving glasses or bowls. Cover and chill in the refrigerator for at least 2 hours, or until set.
07 - Before serving, top each mousse with fresh strawberry halves. Sprinkle with powdered sugar and garnish with mint leaves if desired.