Review:

Honeyed and spiced brandy. Traditionally mixed in equal parts proportions but I prefer slightly drier with a touch more brandy than Bénédictine. The ice will add dilution with time but some, depending on the ice being used, may want to add 10ml (1/3oz) or more chilled water prior to mixing.

History:

Bénédictine and various types of brandy have long been mixed together and combo first enters cocktail books in the early 1900s as a pousse-café layered cocktail with the brandy floated over the liqueur.

BENEDICTINE AND BRANDY
Use cordial glass.
Put in two-thirds Benedictine,
Float one-third Brandy on top carefully so as
not to mix them. Serve.

Raymond E. Sullivan, The Barkeeper's Manual, 1910

However, popular culture has it that the B&B was created "in the 1930s during Prohibition" or more specifically in 1937 by a bartender at New York's famous 21 Club. (U.S. Prohibition ended 5th December 1933).

When, and possibly even where, someone in America first mixed brandy with Bénédictine D.O.M. liqueur is questionable but the popularity of the combination is not. Such was the demand for this cocktail that in 1937/8, Le Palais Bénédictine started production of a bottled blend of 60% Bénédictine and 40% French brandy for sale in the USA under the name Bénédictine B&B. To this day, in the USA, sales of B&B far exceed sales of the original Bénédictine D.O.M. (used in this cocktail).