2 ounces dark rum
1/2 ounce fresh-squeezed lime juice
1/2 ounce simple syrup, or to taste
4-6 ounces fresh ginger beer.
Build the drink in a highball glass filled with ice, adjusting for sweetness and tartness. Depending on when you stop the fermentation of the ginger beer, it may be fully dry or still retain enough sweetness that additional simple syrup is unnecessary. Garnish with a wedge of lime. Serves 1.