Muddle the berries and basil. In a sturdy rocks glass, add 6–8 berries, 5–6 basil leaves, and a small pinch of salt. Gently muddle until the berries release their juices and the basil smells fragrant.
Don’t smash it to bits; you want oils, not bitterness.
Add lemon and sweetener. Pour in 0.75 ounce fresh lemon juice and 0.5–0.75 ounce simple syrup. Stir to mix. Taste—if your berries are very tart, add a touch more syrup.
Add the spirit. Pour in 2 ounces of gin or vodka.
Stir again to combine with the muddled mixture.
Ice and top. Fill the glass with crushed ice. Top with soda water (about 1–2 ounces), then give a gentle stir to lift the color through the drink.
Garnish and serve. Slap a basil sprig between your palms to release aroma, then tuck it in. Add a few berries or a lemon wheel on top.
Serve with a short straw.