Slightly Boozy: The first Commandment of Cool, Matt O’Connor of The Icecreamists says, is, "Keep it simple." The easiest way to make a boozy milkshake, O’Connor says, is to start with a basic recipe for a milkshake, blend it, and toss in some alcohol before it’s finished. "Always underestimate the amount [of alcohol] you think you need — you can add more later," O’Connor says, noting that he starts with a one-to-one ratio of whole milk and ice cream, mixing in a splash of booze later. "Either way, I like it thick and creamy with a big slug of ethanol to cut through the mix."
At Momofuku Milk Bar, Tosi’s rule of thumb is to keep all alcohol additions to less than 3 ounces when dealing with a 12-ounce shake. "There becomes a point when the alcohol will melt the ice cream and turn it into liquid," Tosi says; during recipe development, the team will always start with 1.5 ounces and add additional alcohol in increments of ½ ounce to taste.
Super Boozy: Milkshakes, since they're partially liquid, already work really well when incorporating a good amount of booze. But if you need a little more liquid courage this summer, top it off with an extra shot, or simply serve a milkshake alongside another pour.