In a cocktail shaker, add the 3 thin cucumber slices and 6 mint leaves. Add the simple syrup and fresh lime juice. Gently muddle just enough to release cucumber juice and mint aroma — avoid pulverizing the mint into bitter bits (about 6–8 gentle presses).

Build and shake

Add 2 oz gin (or vodka) and 0.5 oz elderflower liqueur to the shaker. Fill the shaker about two-thirds with ice. Shake vigorously for 10–12 seconds until well chilled.

Double strain

Strain the mixture through a fine mesh strainer (or use a Hawthorne plus fine strainer) into a chilled large coupe or a stemmed glass over fresh ice if preferred. Double-straining removes small bits of cucumber and mint for a clean texture.

Top with sparkle

Gently top the cocktail with 3 oz chilled sparkling wine (or soda water for a lighter version). Pour slowly down the side of the glass to preserve bubbles and create a layered effervescence.

Garnish & serve

Finish with a cucumber ribbon or wheel laid on the surface and a small mint sprig slapped between your palms to release aroma and placed on top. Serve immediately.