01 - Melt the dark chocolate in a heatproof bowl over a pan of simmering water, stirring until smooth. Remove from heat and allow to cool slightly.
02 - In a clean bowl, whip the heavy cream until soft peaks form. Refrigerate until needed.
03 - In another bowl, beat the egg whites with a pinch of salt until soft peaks form. Gradually add the sugar and continue beating until stiff, glossy peaks form.
04 - Stir the egg yolks and vanilla extract into the cooled melted chocolate until fully incorporated.
05 - Gently fold the whipped cream into the chocolate mixture until just combined, maintaining the airy texture.
06 - Carefully fold in the beaten egg whites, one third at a time, until the mixture is smooth and evenly combined.
07 - Spoon the mousse into serving glasses or bowls. Refrigerate for at least 2 hours, or until completely set.
08 - In a small saucepan, combine raspberries, sugar, and lemon juice. Cook over medium heat for 4-5 minutes, stirring frequently, until raspberries break down and sauce thickens slightly.
09 - Remove from heat and strain through a fine sieve to remove seeds. Allow to cool completely.
10 - Spoon raspberry coulis over the set chocolate mousse. Garnish with fresh raspberries and, if desired, a sprig of mint.