At Project Halcyon, the bar sought out ways to use peels—a byproduct from the house Martini, which features clarified banana juice—to use the whole ingredient and avoid waste. According to general manager Adam Montanaro-Taylor, the bar experimented with a host of banana peel garnishes, but in the end, what stuck was this easy-to-make banana skin “oleo.” For at-home bartending, the ingredient could replace simple syrup in a classic Daiquiri or an Old-Fashioned; adding a dash of saline solution makes the banana peel’s subtleties pop.