First documented in Jerry Thomas' 1887 Bartender's Guide. He said, "The name of this cocktail is a misnomer, as coffee and bitters are not to be found among its ingredients, but it looks like coffee when properly concocted, and hence probably its name."
1 1/2 oz Cognac
1 1/2 oz ruby port
1/2 tsp rich (2:1) simple syrup
1 small egg
Shake frantically to emulsify the egg and strain into a cocktail glass. Garnish with a pinch of freshly grated nutmeg.