Drop the sliced strawberries and basil leaves into the bottom of a tall glass. Using a muddler or the back of a wooden spoon, press and twist firmly until the strawberries break down into a rough, juicy pulp and the basil releases its fragrance. This takes about 20 to 30 seconds of steady pressure.

Add the simple syrup and lemon juice directly to the muddled fruit. Stir everything together with a spoon so the syrup coats the fruit evenly and the flavors start to blend.

Fill the glass with ice cubes, packing them in so the drink stays cold all the way to the bottom.

Pour the chilled sparkling water slowly down the inside edge of the glass rather than straight down the center. This keeps the bubbles alive and prevents foam from overflowing.

Give the drink one gentle stir to bring the muddled base up from the bottom without knocking out all the carbonation. Garnish with a fresh basil sprig and serve immediately.