You’ll also need a bottle of champagne if serving during a dinner party.
Bring 600 ml (20 fl oz/2½ cups) of the water to a boil, transfer to large bowl, add the tea bags and allow to infuse for 7 minutes. Remove the tea bags and squeeze them thoroughly above the bowl. Wash the mint and add the sprigs (stalks and leaves intact) to the tea. Bring the remaining water and sugar to a boil in a saucepan and stir until the sugar has dissolved. Add the syrup and the lemon juice to the tea and leave the mixture to fully cool. Once it is lukewarm, place in the refrigerator to fully chill. Remove the mint sprigs. Churn into a sorbet in an ice-cream maker or place the mixture in the freezer and fluff it up every hour with a fork. The sorbet will be ready after approximately 4 hours, depending on your freezer.
For a palate cleanser, fill half a glass with champagne and drop a small scoop of sorbet into the glass. Serve immediately and provide a small spoon.