Fill a chilled rocks glass with ice cubes. Add all ingredients. Garnish with a maraschino berry.
This combination first appeared in 1949, and is ascribed to Gustave Tops, a Belgian barman, who created it at the Hotel Metropole in Brussels in honor of Perle Mesta, then U.S. ambassador to Luxembourg. The cocktail owes its name to the use of vodka, a stereotypical Russian spirit, and the blackness of the coffee liqueur.