In a cocktail shaker, add the fresh strawberries and basil leaves. Muddle gently but thoroughly until the strawberries are broken down and the basil releases its aroma (about 20–30 seconds). Aim for a pulpy mash, not a fine purée.

Combine

Add the gin, elderflower liqueur, fresh lemon juice, simple syrup, and egg white (if using) to the shaker with the muddled fruit and basil.

Dry shake

Without ice, dry-shake the mixture vigorously for 12–15 seconds if using egg white. This emulsifies the egg white and creates a stable foam.

Wet shake

Add the ice to the shaker and shake again vigorously for 12–15 seconds to chill and dilute the drink properly.

Double strain

Double-strain the cocktail into a chilled coupe or martini glass using a fine mesh strainer over a Hawthorne/ julep strainer to remove strawberry seeds and basil bits, yielding a smooth, refined texture.

Garnish & Finish

Float the basil leaf gently on the foam or lay it on the surface. Add a thin strawberry slice to the rim or on the foam. Finish with a light lemon twist expressed over the drink if desired.

Serve immediately. Optionally, offer a short straw so the first sip captures the foam and aroma.