For the brandied cherries, place all of the ingredients aside from the cherries into a medium-sized pot. Bring to a boil, without stirring, over medium heat. Reduce the liquid by half and then add in the brandy. Turn off the heat and add in the cherries. Let cool completely and store in an airtight container in the refrigerator. For best results, let sit for one week before using, up to 2 months.

For the cocktail, place the whiskey, sweet vermouth, brandied cherry liquid, and bitters in a cocktail shaker over ice. Stir until thoroughly chilled. Strain into martini glasses and garnish with a brandied cherry.