Combine the gin, Campari, sweet vermouth, and crème de cassis in a large mixing pitcher. Stir the mixture for about 20 seconds until it feels well chilled.
Fill four rocks glasses with ice cubes. Pour the mixed drink evenly into each glass.
Add three blackberries to each glass as a garnish before serving.
Notes
Chill the mixing pitcher ahead of time so the drink stays cold without extra dilution. If you want a slightly sweeter finish, add an extra half ounce of crème de cassis per serving. The blackberries soften after a few minutes in the glass, so serve right away if you prefer them firm.Course: Drink
Cuisine: Italian
Equipment: Mixing pitcher, Bar spoon, Jigger, Rocks glasses