If using the optional egg white for a silky foam, add the light rum, reposado tequila, Cointreau, lime juice, lemon juice, grapefruit juice, agave syrup, orange bitters and half an egg white to a cocktail shaker without ice. Seal and shake vigorously for 20–30 seconds to emulsify and create a froth.

Wet shake

Add a generous handful of ice (about 1 cup) to the shaker. Shake vigorously for 12–15 seconds until the shaker is thoroughly chilled and slightly frosted on the outside.

Double strain and serve

Double strain the cocktail into the chilled coupe or Nick & Nora glass using a fine mesh strainer over a Hawthorne or julep strainer to remove ice shards and any egg white solids. If you skipped the egg white, just shake with ice and strain once through a Hawthorne strainer.

Garnish & Finish

Express the grapefruit peel over the drink by holding it skin-side down above the glass and giving it a quick squeeze to release oils, then run the peel around the rim and drop it into the drink or skewer it on the cocktail pick and lay across the glass.

For a festive, shimmering finish, very lightly dust the top of the foam (or surface) with a pinch of edible glitter or superfine sugar. Serve immediately.