First, prepare the cranberry concentrate. Pour 2 cups of cranberries, the cranberry juice, water, and brown sugar into a saucepan and bring to a simmer. Let simmer on low for 5 minutes, until the cranberries have bursted. Stir frequently.

Use a fine mesh strainer to strain the cranberry concentrate. Use a rubber spatula to press as much of the concentrate as possible through the strainer. Then let then concentrate cool.

To mix the cranberry moscow mule, pour the concentrate, lime juice, ice, ginger beer, and vodka into a large container. Gently stir. Add the remaining cranberries and slices of lime to garnish.