There's no rule that says warm-weather cocktails must be served with tiny umbrellas. We updated this tiki-bar fave of St. Germain liqueur, vodka, lychee juice, and lemon juice with an unexpected garnish, a slice of fresh lychee on the side of glass.
Puree lychees in a blender until smooth. Transfer to a sieve set over a bowl; stir and press on solids to drain as much liquid as possible. Discard solids and refrigerate juice until cold, at least 30 minutes.
To assemble cocktail, fill a highball glass with ice, pour 3 ounces lychee juice, vodka, St. Germain, and lemon juice over ice. Top off with seltzer; gently stir to combine. To garnish, slice whole lychee in half and rest on the side of the glass; serve immediately. Reserve extra lychee juice for additional cocktails.