Combine the water and sugar in a small saucepan over high heat. Stir so that some of the sugar dissolves, then add the frozen cranberries.
Bring the pot to a boil, stirring periodically to help the sugar dissolve.
Once boiling, stir to ensure all of the sugar has dissolved, then remove from heat. Stir in the fresh rosemary (stems and all!) and cover the pot.Steep for about 1.5 to 2 hours while it cools.
Use a fine mesh strainer to transfer the liquid into a jar. Seal and cool in the fridge for at least 30 minutes to 1 hour before using in cocktails.
Notes
Frozen cranberries: You can use the cranberries straight from the freezer, since you’ll be bringing the mixture to a boil before it steeps.Storing simple syrup: You can keep simple syrup in the fridge for up to 1 month. We like storing homemade simple syrup in a mason jar.Cocktail ideas: This flavorful simple syrup is perfect for festive Thanksgiving and Christmas cocktails! Use it in a holiday cocktail recipe like our Mistletoe Mule. Or, make a holiday themed margarita with it instead of using regular simple syrup or agave. You can even use it to sweeten a simple drink like a vodka cranberry, if you’re craving something a little more festive for the winter season.