1/2 cup (4 ounces) hot water, just boiled, plus additional water to warm the mug
1 1/2 ounces dark rum, such as Gosling’s Black Seal
1/2 ounce ginger liqueur, preferably Domaine de Canton
Twist of lemon peel
Warm a cup or mug with a little of the just-boiled water; swirl and discard.
Add the rum and ginger liqueur. Stir in the 1/2 cup of just-boiled water. Twist the lemon peel over the cup to release its oils, then drop it in.