3-4 cubes of seedless watermelon (about 1x1x1 inch)
1.5oz of fresh lime juice
1.5oz of simple syrup (recipe here)
1.5oz of white rum
4-5 mint leaves
Splash of club soda (added after shaking)
Put the cubes of watermelon in the shaker, then muddle (mash) them to release the watermelon juice. We have a special tool that looks like a tiny potato masher, but you can improvise with the handle of a kitchen spoon. Watermelon mashes pretty easily.
Once you have the watermelon muddled, add the other ingredients to the shaker along with crushed ice and give it several hard shakes.
Pour the liquid into a tall ice-filled glass and add a splash of club soda for a bit of fizz. Garnish with a thin lime wedge to finish it off.