01 - Set a heatproof bowl over a pot of gently simmering water to create a double boiler. Add the chopped dark chocolate and stir constantly until completely melted and smooth. Remove from heat and allow to cool slightly while preparing other components.
02 - In a chilled mixing bowl, combine the cold heavy cream with vanilla extract. Beat using an electric mixer or whisk until soft peaks form. Transfer to the refrigerator to maintain its structure until ready to fold.
03 - In a clean bowl, beat the egg whites with a pinch of salt until soft peaks begin to form. Gradually sprinkle in the granulated sugar while continuing to beat until stiff, glossy peaks develop. Set aside.
04 - Stir the separated egg yolks into the slightly cooled melted chocolate, mixing vigorously until completely incorporated and the mixture becomes thick and glossy.
05 - Gently fold one-third of the chilled whipped cream into the chocolate base to lighten it. Add the remaining cream and fold with a spatula using sweeping motions until no white streaks remain.
06 - Add the beaten egg whites in two portions, folding carefully after each addition. Use a light hand to preserve the airiness and volume of the mousse.
07 - Distribute the mousse evenly among 4 serving glasses or ramekins. Cover with plastic wrap and refrigerate for a minimum of 2 hours until fully set and firm.
08 - Just before serving, toss the halved strawberries with powdered sugar if desired. Arrange the sugared strawberries on top of each chilled mousse and finish with fresh mint leaves as an elegant garnish.