01 - Combine raspberries, sugar, and lemon juice in a medium saucepan. Cook over medium heat, stirring frequently, until berries break down and mixture thickens approximately 5 to 7 minutes. Press through a fine mesh sieve to remove seeds. Allow to cool completely.
02 - Place chopped chocolate in a heatproof bowl. Melt over a saucepan of simmering water using a double boiler method, or microwave in short bursts while stirring until completely smooth. Cool slightly before proceeding.
03 - In a clean bowl, whip egg whites with a pinch of salt using an electric mixer until soft peaks form. Gradually add sugar and continue beating until stiff peaks form.
04 - In a separate bowl, whip chilled heavy cream to soft peaks using an electric mixer. Stir in vanilla extract gently.
05 - Whisk egg yolks into the lukewarm melted chocolate until the mixture is smooth and well combined.
06 - Gently fold the whipped cream into the chocolate mixture using a spatula, maintaining the light texture throughout the folding process.
07 - Carefully fold the beaten egg whites into the chocolate mixture in two additions, using gentle folding motions to preserve the mousse's airy consistency.
08 - Spoon a layer of cooled raspberry purée into the bottom of each serving cup or glass. Top with chocolate mousse. Repeat layers if desired for additional depth.
09 - Refrigerate the assembled cups for at least 2 hours until the mousse is fully set and firm.
10 - Remove from refrigerator and top each cup with fresh raspberries, dark chocolate shavings, and mint leaves if desired. Serve immediately.