To rocks glass, add 6 kumquat halves and sugar. With a toothpick, skewer remaining 2 halves of kumquat for garnish. Using spoon or muddler, mash kumquat with sugar until juices are released. Add ginger, rum, and ice, then stir to mix. Top up with club soda, and garnish with kumquat skewer.
Adapted from TheKitchn.com
Watch this video