If you don't have honey syrup ready, combine equal parts honey and hot water and stir until smooth. If the Seville orange marmalade is thick, weigh out 0.5 tsp and stir with a small splash of warm water (about 1/4 tsp) to loosen to a spoonable, pourable consistency.

Combine ingredients

In a shaker without ice, add gin, blood orange juice, lemon juice, Cointreau, the loosened Seville marmalade, honey syrup, bitters, and egg white. The use of egg white is optional but recommended for a silky texture and good foam; use pasteurized egg white if concerned about raw eggs.

Dry shake

Seal the shaker and shake vigorously without ice for 12–18 seconds. This emulsifies the egg white and integrates the marmalade for a uniform texture and a dense foam.

Wet shake

Open the shaker, add a large handful of ice (or fill to 3/4), reseal and shake vigorously for 12–15 seconds until the shaker is cold to the touch and slightly frosted.

Strain

Double-strain the cocktail into a chilled coupe or Nick & Nora glass using a Hawthorne strainer and a fine mesh strainer to remove ice shards and any citrus pulp or marmalade bits. This yields a smooth, silky drink with a clean foam head.

Garnish & Finish

If you like a sugared rim, wet the edge of the glass with a small piece of orange and dip lightly into coarse sugar before pouring.

Express the orange oils: hold the orange zest or a thin orange slice about 4–6 inches above the drink, skin-side down, and give it a firm twist to spray the essential oils across the foam. Rub the expressed peel gently on the rim, then place the blood orange wheel or Seville slice on the rim or floated on the foam.

Optionally add a final tiny drop (1 drop) of Angostura bitters onto the foam and drag a cocktail pick through it for a decorative pattern.

Serve immediately. The Seville Sunset is best enjoyed fresh while the foam is still present and aromatics are lively.