Warm the lemon juice, 1 1/2 cups (360 ml) water, and the sugar to boiling. Stir until the sugar is completely dissolved.

Roughly tear the basil leaves and put them in a small bowl. Pour the lemon juice mixture over the basil leaves and let steep for at least 15 minutes.

Pour the orange juice into a small saucepan and sprinkle the gelatin over its surface. Let the gelatin soften for 5 minutes, then warm the pan over medium heat, stirring frequently, until the gelatin is fully dissolved.

Strain the basil out of the lemon juice and whisk the juice into the gelatin mixture.

Pour the liquid into six small cups or a 1-quart (1-L) dish. Refrigerate for 2 hours, or until softly set. Garnish with whipped cream and basil leaves to serve.