If using egg white, separate one egg and reserve the white. Chill a coupe or small Nick & Nora glass by filling with ice water while you mix the drink.

Add bourbon (2 oz), cognac (1/2 oz), fresh lemon juice (3/4 oz), fresh grapefruit juice (1/4 oz), simple syrup (1/2 oz), 2 dashes orange bitters and 1 dash Angostura bitters to a cocktail shaker.

If using egg white, add the egg white to the shaker. Do a dry shake (no ice) vigorously for 12–20 seconds to emulsify and build foam.

After the dry shake (or immediately if not using egg white), add 1 cup of ice to the shaker and shake vigorously for 12–18 seconds until the shaker is chilled and the exterior is frosty. This both chills and dilutes the cocktail to balance the flavors.

Discard the ice water from the chilled glass and double-strain the cocktail through a Hawthorne strainer and a fine mesh strainer into the chilled coupe. Double-straining removes small ice shards and any egg white solids for a smooth texture.

Express the oils from a large grapefruit or orange twist over the surface of the drink by holding the twist over the glass and pinching so the citrus oils spray onto the cocktail. Rub the peel around the rim, then drop it into the drink or rest it on the rim.

Optional: grate a small amount of nutmeg or additional citrus zest over the foam for aroma. Serve immediately.