
Coffee liqueur is a sweetened spirit infused with roasted coffee, ranging from dark, syrupy styles to lighter, more bitter ones.
It sweetens a drink and adds coffee flavor and body, usually as a modifier rather than the base. It is the key modifier in the Espresso Martini, so its sugar level sets that drink's balance.
Another coffee liqueur
Swaps straight in. If replacing sweet Kahlúa with a drier one, add about a barspoon of 2:1 syrup per 30 ml. Use less syrup with a sweeter liqueur.
Homemade coffee liqueur
Mix 2 parts vodka, 2 parts 2:1 syrup and 1 part cold espresso. It lands close to Kahlúa in strength and sugar.
Coffee-flavored vodka
Use half the measure and make up the rest with 2:1 syrup to land near a liqueur.
Sugar preserves as surely as alcohol, so an opened bottle keeps for years; what fades is the coffee aroma. In the cold, sugar can crystallize at the bottom; gentle warmth and a shake dissolve it again. Keep it out of direct sun, which fades both color and aroma.