To a cocktail shaker, add the blackberries and mint leaves. Muddle them until the berries are well broken down. The mint should be mostly intact. Muddling mint too much can cause a bitter aftertaste.
Add simple syrup (or sugar) and bourbon and fill the shaker with ice. Using a long spoon, stir vigorously until very cold.
Fill a glass with ice. Use a fine strainer or a cocktail strainer to pour the bourbon mixture into the glass. Fill the rest of the glass with club soda. Garnish with a lemon wedge, blackberries, and a fresh mint sprig if desired.
Notes
What Bourbon to Use: Use what you like best. Examples of midgrade bourbons are Basil Hayden, Wild Turkey, Maker’s Mark, Four Roses, Knob Creek, and Jim Beam.More Tips:
If you don’t have a jigger, one fluid ounce equals to two tablespoons.
If you garnish with a fresh mint sprig, slap it gently a few times against your palm. This releases the aromatic oils but won’t flavor the drink (and you look like a pro!).
If you use less ice or no ice, consider using 3 ounces because you will be adding more juice to fill the drink.
Don’t smash the mint leaves too much as this will make the drink bitter. You just want to rub them enough to release the mint flavor.