Bols Liqueur Monastique

Monastic liqueur is a generic category for domestic or imported herb and spice liqueurs produced in the style/imitation/inspiration of old medicinal potions produced by religious orders. The flavor profile of these products can be significantly dissimilar. Generally, the proof tends to be around 40º, so these are usually rich, full strength liquors. The definitive example of a monastic liqueur is Chartreuse, but both green and yellow Chartreuse expressions are profundly important in mixology and are called for by name in mixed drinks. It is rare—but not unheard of—for a cocktail recipe to simply call for a “monastic liqueur”. These aren’t necessarily brand calls, although they could be, since some of these products literally said “monastic liqueur” on the label. What they are probably not calling for is Chartreuse, because they would have called for it by name, and most other monastic liqueurs are at least marginally less assertive. (i.e., Benedictine is probably a better substitute than Chartreuse in these situations.) Otherwise, you must rely on your discretion.