One balmy night at an artist's retreat in Umbria, my host offered me the syrupy walnut-infused liqueur nocino. I sipped one small, dark glass and then another and have been hooked on it ever since. Nocino must be made with unripe walnuts only, and tradition holds that they must be gathered on June 24, the Feast of San Giovanni. Macerated in sugar and spices, the nuts are steeped in a neutral spirit to extract their flavor. When I returned to the States, I took up the hunt for nocino and was pleased with what I found. My favorite is Aggazzotti Notte di S. Giovanni ($50), produced on an estate in Modena. Aged for five years, it has an intense nuttiness and is as easy to drink as a fine port—though at 80 proof, it packs a punch. On the sweeter side, Nocino Antica Distilleria Russo ($35) from Italy's Campania region has pronounced flavors of clove and cinnamon; I like to drizzle it over vanilla gelato. There are also domestic takes on the Italian tradition. Made in Napa Valley, Monteverdi Spirits' delicate nocino ($30) has an ethereal vanilla finish; over ice with a squeeze of lemon, it's a great aperitivo, and it mixes well with cocktails, too.