Place the raspberries, sugar, and lemon juice in a blender or food processor. Puree until smooth.

Pour the puree through a fine-mesh sieve into a small bowl, pressing with the back of a spoon to extract the juice and remove the seeds. Discard the seeds.

In a microwave-safe bowl, combine the white chocolate and 2 tablespoons of the heavy cream. Microwave in 20-second intervals, stirring in between, until completely melted and smooth. Let it cool for 5 minutes.

Stir the raspberry puree into the melted white chocolate until fully combined.

In a large, chilled mixing bowl, beat the remaining heavy cream and vanilla extract with an electric mixer until stiff peaks form.

Gently fold the raspberry-chocolate mixture into the whipped cream using a rubber spatula. Use a cutting motion to keep the mixture airy; do not overmix.

Spoon the mousse into serving glasses or ramekins.

Refrigerate for at least 2 hours to set before serving. Garnish with fresh berries and mint.