1. Reserve a few berries for garnish. Purèe the remaining berries and sugar in a food processor or blender. Strain through a sieve to remove any seeds. The purèe should be quite thick. Add the lemon juice.

2. Whisk the cream in a chilled bowl until soft peaks form. Whisk the mascarpone in another bowl to soften it. Fold the mascarpone into the cream. Stir half of the berry purèe into the cream mixture.

3. Divide the berry purèe among 4 glasses and top with the cream mixture. Garnish each with the reserved berries and a mint leaf. Refrigerate for at least 2 hours, until chilled. Serve cold.