Preparation Mix first 4 ingredients in large pitcher; stir until well blended. Refrigerate until cool, about 2 hours. (Can be made 1 day ahead. Keep refrigerated.) Stir again and divide mixture among 6 glasses. Top with bitters, garnish with rosemary sprigs, and serve.
Preparation Mix first 4 ingredients in large pitcher; stir until well blended. Refrigerate until cool, about 2 hours. (Can be made 1 day ahead. Keep refrigerated.) Stir again and divide mixture among 6 glasses. Top with bitters, garnish with rosemary sprigs, and serve.