Begin by combining the chopped chocolate and cold butter in a double boiler over simmering water. Stir continuously until melted and smooth. If you’re using a microwave, heat in 30-second intervals, stirring in between, until fully melted. Set aside to cool slightly.
In a medium bowl, whisk the egg yolks. Once the chocolate mixture has cooled slightly, gradually add it to the egg yolks while continuously whisking to prevent the yolks from cooking. Set this mixture aside.
In a separate mixing bowl, using an electric mixer, beat the egg whites until they begin to froth. Gradually add the granulated sugar, continuing to whip until soft peaks form. This should take about 3-5 minutes.
Gently fold the whipped egg whites into the chocolate mixture. Start with a third of the egg whites to lighten the mixture, then carefully fold in the remaining whites until no streaks remain. Take care not to deflate the mixture.
Spoon the chocolate mousse into serving dishes. Cover with plastic wrap and refrigerate for at least 2 hours, or until set.
Before serving, top each mousse with a generous dollop of homemade whipped cream and a sprinkle of fresh berries. Enjoy your decadent chocolate treat!
