These refreshing cocktails are perfect for summer entertaining!
Place metal mint julep cups in the freezer to chill before serving.
In a bowl, combine berries with granulated sugar. Let stand for 30-45 minutes, stirring every 15 minutes, until berries release their juices and form a syrup. Strain mixture through a fine-mesh sieve, pressing on berries to release juices. Discard solids. You should have about 1/2 cup blackberry syrup.
Place 2 tablespoons blackberry syrup in each julep cup. Add 1 tablespoon lemon juice and 6 mint leaves to each cup. Muddle the mint leaves into the syrup in each cup just until lightly crushed (don't overdo it, or the mint will become bitter).
Add 3 ounces (1/3 cup) bourbon to each cup and fill with crushed ice. Stir until the cup starts to look frosty on the outside. Add additional ice to the cup to fill. Serve, garnished with mint leaves, curled lemon peel, and additional berries, if desired.