01 - In a small saucepan, combine raspberries, 2 tablespoons granulated sugar, and lemon juice. Cook over medium heat, stirring occasionally, until the raspberries soften and the mixture thickens, approximately 5 to 7 minutes. Pass the cooked raspberry mixture through a fine-mesh sieve to remove seeds. Set aside to cool completely.
02 - Place the chopped semi-sweet chocolate in a heatproof bowl. Melt the chocolate either over a saucepan of simmering water (creating a double boiler) or in a microwave using short intervals, stirring until smooth. Allow the melted chocolate to cool slightly.
03 - In a meticulously clean mixing bowl, whip the egg whites with a pinch of salt until soft peaks begin to form. Gradually incorporate 3 tablespoons granulated sugar, continuing to beat until stiff, glossy peaks are achieved.
04 - In a separate, chilled bowl, whip the cold heavy cream until it forms soft peaks. Stir in the pure vanilla extract.
05 - Whisk the egg yolks into the slightly cooled, melted chocolate until the mixture is smooth and evenly combined.
06 - Gently fold the whipped cream into the chocolate-yolk mixture, being careful not to deflate the cream.
07 - Delicately fold the beaten egg whites into the chocolate mixture in two additions, ensuring the mousse maintains its airy and light texture.
08 - Spoon a layer of the prepared raspberry purée into the bottom of each individual serving cup or glass. Carefully top with a generous layer of the chocolate mousse. Repeat the layers if desired, creating an attractive presentation.
09 - Refrigerate the assembled mousse cups for a minimum of 2 hours, or until the mousse is thoroughly set and firm.
10 - Just before serving, adorn each mousse cup with fresh raspberries, delicate dark chocolate shavings or curls, and an optional mint leaf for an elegant finish.