For a variation, Day-Lewis sometimes fills the glasses halfway up with the syllabub, adds a little raspberry purée or a few chopped white peaches or strawberries, and then tops them off with the remaining syllabub, to create a fruity middle section to the dessert. Put 1⁄3 cup superfine sugar, 1⁄4 cup oloroso sherry, 2 tbsp. cognac, 2 tbsp. fresh lemon juice, and the zest of 1 lemon into a large bowl. Stir well, then cover and let sit out at room temperature overnight to allow the flavors to meld. Add 1 3⁄4 cups plus 2 tbsp. cold heavy cream (preferably unhomogenized) and a pinch of freshly grated nutmeg (just "a suspicion", says Day-Lewis) to the sherry mixture and whip with a whisk until soft peaks form. Spoon into 4 glasses and garnish each with a bit of lemon zest and a sprig of rosemary. Serves 4.