Pisco is a South American grape brandy popular in Peru and Chile. If you can't find it in your area, feel free to substitute white tequila, grappa, or vodka. Don't be alarmed by the strength of this new classic; it's a cocktail that's meant to be sipped and savored.
Makes 4 servings
1. Process blackberries in a blender until smooth. Pour through a wire-mesh strainer into a 1-qt. jar with a tight-fitting lid, discarding solids.
2. Add pisco and next 3 ingredients to jar. Cover with lid, and shake vigorously 30 seconds or until foamy. Pour mixture into 4 (10-oz.) glasses filled with ice. Top each with a dash of bitters, if desired. Serve immediately.