Pre-chill a coupe glass.
Prepare a lemon zest twist and set aside.
Combine cognac, sweet red vermouth, gomme syrup, and Angostura bitters in a mixing glass with ice.
Stir well for approximately 20–25 seconds until properly chilled and diluted.
Strain into the chilled coupe glass.
Top with a small splash of soda water.
Express the lemon zest twist over the surface of the drink, run it around the rim, and place it on the glass as garnish.
The Harvard Cocktail first appeared in George Kappeler's 1895 'Modern American Drinks' and is essentially a cognac Manhattan - the small addition of soda water is period-accurate and helps lift the aromatics without diluting the drink's character.
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