Muddle blackberries and sugar in a cocktail shaker. Add basil and lightly muddle until fragrant. Add gin and lemon juice then fill shaker with ice, secure lid, and shake vigorously until thoroughly chilled. Strain into a Collins glass filled with ice and top off with chilled club soda. Garnish with blackberries and basil leaves.

Muddle blackberries and sugar in a cocktail shaker. Add basil and lightly muddle until fragrant. Add gin and lemon juice then fill shaker with ice, secure lid, and shake vigorously until thoroughly chilled. Strain into a Collins glass filled with ice and top off with chilled club soda. Garnish with blackberries and basil leaves.