This delicious sorbet takes a little more time than usual to make as the alcohol in the champagne makes it tricky to freeze. It is far easier to make this in an ice cream machine but you can do it by hand, bearing in mind that it will take twice as long as a non-alcoholic sorbet. It keeps well in the freezer for up to two months.
900ml of bottled water, 900g of sugar, 900ml of Cassar de Malte, the zest of one lemon, two tablespoonfuls of finely chopped fresh mint.
Dissolve the sugar in the water over low heat, then turn up the heat to bring the pot to the boil and let it bubble vigorously for five minutes. Allow it to cool, then stir in the rest of the ingredients and pour this into the ice-cream maker, following the instructions to make sorbet. Otherwise, pour it into a shallow freezerproof bowl and freeze it, taking it out of the freezer at intervals to whisk it as it freezes, making smooth and soft ice-crystals rather than large, hard ones.