This old-fashioned, refreshing summertime drink is adapted from Sally Lesh's Gustavus Inn Cookbook. Try pouring some over ice cream or add a tablespoon or two to berry pie filling.
1. In a nonreactive bowl, pour vinegar over raspberries. Let stand, covered with a clean cloth or cheesecloth, for 24 to 48 hours (the mixture will become very strong smelling). Strain with a fine-mesh sieve, carefully pressing on the solids to extract as much liquid as possible. Discard seeds. Measure liquid (there should be about 2 cups).
2. In a medium saucepan, add liquid and for every 2 cups liquid, 1 scant cup sugar. Bring to boil, reduce heat, and simmer for 20 minutes. Cool, pour into glass jars, and cover tightly. As it ages, the shrub will take on a syruplike consistency. Keep in a cool dark place until needed; raspberry shrub will keep for months if refrigerated.
3. To serve: In a tall glass filled with ice cubes, pour 2 tablespoons shrub; fill glass with cold water, seltzer water, lemonade, or ginger ale.
Makes 2 cups