Pink Grapefruit–Champagne Sorbet Cocktail

There’s nothing I like better than very, very cold Champagne. So cold that I usually drop a small ice cube into my glass to make sure it’s as chilled as possible. I always feared that it was offensive and crass to ice down Champagne until I went to a tasting of Krug Champagne, considered by many to be the finest of them all. I didn’t dare drop an ice cube into any of the glasses that were presented to me, but I did confide that I often did so to one of their experts, who surprised me by saying that it’s perfectly acceptable to put a bit of ice in Champagne for the very reason I do it. For this sorbet, you don’t need to use the finest French Champagne. In fact, I’ve made it successfully with Italian prosecco and Spanish cava—without offending anyone.