Add the coarsely chopped Granny Smith apple, lemon zest and lime zest to the syrup. Reduce heat to low and simmer gently for 6–8 minutes until the apple softens and the syrup takes on apple flavor.

Remove from heat and let steep 15 minutes to extract more citrus and apple aromatics.

Strain the syrup through a fine mesh sieve, pressing on the apple solids to extract as much liquid as possible. Discard solids. Cool the syrup to room temperature and refrigerate in a sealed container. Yields roughly 5–6 oz; use 0.5 oz per cocktail.

Cocktail

Build and shake

Chill a flute or coupe glass in the freezer or fill with ice water to chill. In a cocktail shaker, add 1.5 oz gin, 0.5 oz Calvados, 0.5 oz fresh lemon juice, 0.25 oz fresh lime juice, 0.5 oz chilled citrus-apple syrup and a handful of ice (about 1 cup).

Shake vigorously for 10–12 seconds until well chilled and slightly diluted.

Strain and top

Discard ice water from the chilled glass if used. Double-strain the shaken mixture into the chilled flute or coupe (to remove any ice shards and pulp).

Top gently with 2.5 oz chilled sparkling wine or dry prosecco. Pour slowly down the side to preserve bubbles and create a light effervescent lift.

Garnish

Express a lemon twist over the surface to release oils, wipe the rim with the twist and drop it in or set on the rim along with a thin apple slice or fan. Serve immediately.