For this drink I wanted to highlight that wonderful summer fruit, the watermelon. Here I use a gastrique which adds a wonderful complexity in the form of vinegar. A drier light rum like Banks 4 year keeps the results from being entirely too sweet, although feel free to up the lime a little to balance out the sugar.
1.5 oz Banks 4yr rum
.5 oz watermelon gastrique (see below)
.5 oz lime
Shaken and poured over ice in a rocks glass. Top with soda and garnish with a lime wedge. (Note: the gastrique is very viscous so be sure to get the full .5 oz out of your jigger.)
Combine one part fresh watermelon juice with one part white vinegar and four parts sugar (to juice watermelon simply blend chunks of fresh melon and strain out the pulp). Heat the mixture to a simmer and reduce by about 1/8. You want it to be syrupy but still pourable. This should keep for up to a month in the fridge.