Pour lingonberry syrup into the bottom of the glass. Stir in lime juice and vodka.
Fill a Collins glass or a mule mug with crushed ice, then slowly pour in the ginger beer. Garnish with a lime slice, if desired. Serve, stirring gently before drinking.
Notes
If you can't find the syrup, substitute your own syrup made from lingonberry jam or another flavor of tart jam such as cranberry or blackberry.On the stove over medium heat, bring to a boil ½ cup water and ½ cup granulated sugar. Lower heat and stir in ½ cup jam. Stir for two minutes. Remove from heat. Allow to cool completely. Strain out any chunks through a sieve before using. Store in a jar or other airtight container for up to 1 month.