Cosmo Syrup

Directions

1. 1
   Bring sugar and 1 cup water to a boil in a medium saucepan and cook until sugar is completely dissolved, about 1 minute.
2. 2
   Remove from heat, stir in zests, and let sit at room temperature for 30 minutes to infuse syrup.
3. 3
   Strain to remove zests, then stir in juice, Cointreau, and vodka.
4. 4
   Refrigerate syrup, covered, until cold.
5. 5
   For each cosmo, pour 2 tablespoons syrup over 1/2 cup crushed ice.