Add one cup water, one cup sugar and one cup halved and seeded kumquats to a small saucepan. Bring to a boil and then muddle kumquats and simmer for 2 minutes. Remove from heat and add three sprigs of lemon thyme. Transfer syrup to a bowl and refrigerate.
Add ice to a cocktail shaker, pour in two oz of the syrup, one oz of gin, one oz of Grand Marnier and add one sprig of lemon thyme. Shake well and serve in a coupe glass. Garnish with a kumquat and thyme.