To make the lemon-basil syrup, wash and dry 6 large basil leaves. Put them in a small saucepan with 1/2 cup (100 g) sugar and 1/2 cup (125 ml) water, and add the zest of one lemon (unsprayed). Heat the mixture, pressing the basil with the back of a spoon as you heat the syrup, stirring a bit, to encourage the leaves to release their flavor and the sugar to dissolve. As soon as the syrup just begins to boil, remove from heat and let cool completely. Once cool, strain the syrup into a jar and refrigerate until ready to use. The lemon-basil syrup will keep for up to one month. Makes about 3/4 cup (180 ml.)