Who says bartenders aren’t looking out for our health? Lately, a fair number seem dead earnest in making sure that patrons get their daily allowance of calcium.

Milk punch, a sweet, cold, elegant blend of dairy and liquor that dates back centuries, has become a hot item on bar menus across the nation. A California milk punch, which typically calls for rum, spices and a rumlike spirit called Batavia arrack, holds down a place at the Coachman, a fledgling San Francisco restaurant where most of the cocktail selections hail from the 19th century, and at Underdog, a new subterranean tavern under the Growler in Lower Manhattan.

Punch House, which opened in the Pilsen neighborhood of Chicago last year, ladles out an ancient brandy-based formula known as Mary Rockett’s Milk Punch. Eastern Standard, a Boston bar, changes its milk punch recipe every few months, and the New York restaurant Betony offers a different milk punch even more often. Play, the new cocktail bar associated with the Museum of Sex, in Midtown, has a Korovazon Milk Punch made with pisco.

These drinks are not creamy, like the brandy or bourbon milk punches common in New Orleans; they are clarified elixirs. Cold ingredients are combined with hot milk so that the milk curdles; the blend is filtered repeatedly until the liquid becomes clear. This can take hours. Then, typically, the punch rests for a day or so until served. If you don’t have the time, you don’t have this punch.