Add 2 oz aged rum, 0.5 oz dark rye or blended whiskey, 0.5 oz Cointreau, 0.75 oz fresh lime juice, 0.5 oz fresh grapefruit juice, 0.5 oz demerara syrup, and 2 dashes Angostura bitters into a cocktail shaker.

Add ice and shake

Fill the shaker with ice (enough to nearly fill). Seal and shake vigorously for 10–15 seconds until the outside of the shaker is very cold and well-chilled.

Prepare glass

Place a large ice cube or sphere into an old-fashioned (rocks) glass.

Strain

Double-strain the shaken mixture over the large ice cube into the prepared glass using a Hawthorne strainer and a fine mesh strainer to remove small ice shards and pulp for a silky texture.

Brightener & Finish

Express oils

Hold an orange peel about 6 inches above the drink, skin side down. Give it a strong squeeze to express the oils across the surface of the cocktail, then rub the peel on the rim and drop it into the glass.

Optional grapefruit twist

If using, express a grapefruit twist in the same way and set on top of the drink for a bright citrus aroma.

Serve immediately and enjoy the balanced interplay of aged rum, spice from the rye, citrus brightness, and demerara sweetness.