Muddle the berries: In a cocktail shaker, add 6–8 blackberries and 1/2–3/4 ounce simple syrup (or honey).
Gently muddle until the berries break down and release their juices.
Add the base: Pour in 2 ounces bourbon and 3/4 ounce fresh lemon juice. Add a handful of ice.
Shake it cold: Shake for about 10–12 seconds until the shaker feels frosty. This chills and dilutes the drink just enough.
Strain: Double-strain into a rocks or Collins glass filled with fresh ice.
Use a fine-mesh strainer to catch seeds and pulp.
Top with bubbles: Add 2–3 ounces of sparkling water, club soda, or prosecco. Stir gently to combine.
Garnish and serve: Add a few whole blackberries, a lemon wheel, or a mint sprig. Serve immediately while it’s crisp and effervescent.