4 teaspoons grated fresh ginger
1 teaspoon aromatic bitters such as Angostura
2 tablespoons fresh lime juice
1/2 cup light rum (optional)
12 ounces ginger beer
Put 2 tsp. ginger, 1/2 tsp. bitters, and 1 tsp. juice into each of 2 tall cocktail glasses. Fill both glasses with ice. Add rum (if using), dividing evenly, and top each glass with ginger beer.
Note: Nutritional analysis is per serving.