Place the castor sugar and water into a saucepan over medium heat and slowly bring to a boil. Allow to simmer for a few minutes to thicken slightly, then remove from the heat and stir in the lemon juice, zest and Limoncello and allow to cool completely.

Churn in an ice cream machine, if you have one. Alternatively, simply pour the mixture into an ice tray and freeze. Once frozen, pop the cubes in a blender and blitz until you have a smooth purée.

Normally, you would serve it immediately, but for the sake of this recipe, pour the purée into a Tupperware and freeze. Use a melon ball scoop to make small sorbet balls and place these back into the freezer and freeze until solid.

Half an hour before serving your dessert, place the champagne glasses in the freezer. As your guests arrive, pop 2 or 3 balls in each champagne glass and top up with ice-cold champagne.

Tips: The sweetness of your lemons will vary, so you may need to adjust the ratios to taste once everything is combined.

For an even smoother sorbet, after blending it for the first time, you can spoon the purée back into the ice tray to freeze and purée once again.

Alternatively, raspberry sorbet is equally delicious in champagne.