This unusual and refreshing sorbet is so light it is best eaten within two days of making. More or less sugar and lemon may be added according to your taste, and depending on whether the sorbet is to be an appetizer or a dessert.
In a medium saucepan, heat the water and sugar until dissolved to a syrup. Boil steadily for 2-3 minutes. Divide the syrup in half. Add the lemon zest to one portion and simmer it over very low heat for about 10 minutes. Add the lemon juice and let the syrup cool.
Immerse the rosemary sprigs in the remaining syrup. Bring the syrup to a boil, turn down the heat