The Preparation
Make rosemary simple syrup by simmering rosemary sprigs in equal parts sugar and water, then cool.
Muddle blackberries and blueberries in a shaker.
Add gin, lemon juice, and rosemary simple syrup with ice.
Shake well and strain into a glass over ice.
Top with sparkling water and garnish with a fresh rosemary sprig and berries.
