City wall: A District mural at P.J. Clarke’s
 
  Sidecar also sports a mean menu that includes this crab and corn chowder
 
  Sidecar’s namesake

It is lunchtime in Washington, and the usual hustle is in full swing at P.J. Clarke’s. Tables are loaded with plates of food; servers and bussers make haste with carefully stacked dishes; glasses clink, the occasional spill is wiped away; the decibel level of chatter rises. It’s the happy chaos of diners on a mid-day break.

Clandestine Cool at P.J. Clarke’s
But we suggest you skip it. Head downstairs instead. Trip the hidden sliding door, step inside, and find yourself at Sidecar (1600 K St. NW, 202-463-6630), P.J. Clarke’s private dining room and bar, and an oasis of white tablecloths, familiar barkeeps, nostalgic décor, flattering light, and hushed conversation. This isn’t a dine-and-dash kind of place; it’s a spot for regulars, power brokers, a clublike atmosphere with a distinct members-only vibe. Chilled cocktails are the norm, and a familiar accompaniment to a filling lunch or dinner. Sidecar is one of several DC dining establishments taking cues from the past, nodding to clandestine cool and speakeasy chic. Fitting, as Prohibition-era Washington was something to behold and anything but a model dry city: Up to 3,000 illegal speakeasies were in operation during the Thirteen Awful Years, as H.L. Mencken called them—up to 10 times the number of legal saloons that operated before. Even Congress employed its own bootleggers. Washingtonians prided themselves on being wet, and not much has changed since.

The influence of that era has slowly made its way back to the fringes of the mainstream. The bonus of gourmet grub sets Sidecar apart, a place that, despite its speakeasy roots, is all about the three-hour meal—with a side of high-quality cocktails, of course. This is, after all, not the type of place where anyone passes judgment on day-tonight sipping. “It’s like a men’s club, but for both men and women,” says Jewels Kennedy, Sidecar’s manager. Here regulars are treated with respectful familiarity, and many can be found occupying the leather banquettes on a daily basis. Some even have their names stenciled on plaques.

Once you have found Sidecar, which opened last year as an offshoot of the original New York location, which opened its doors in 1884, it’s hard to stray from the timeless charm. The menu offers an array of comfort-food favorites: fresh crab and corn chowder, juicy cuts of meat, salmon served on a bed of seasonal vegetables. The dining room’s namesake cocktail, which was invented during Prohibition, is an appropriately lovely creation of Cognac, Cointreau, and lemon juice, with a sugar rim. Sidecar also is open to members only from 3 to 5 pm— like a late-afternoon Starbucks run, only with mixed drinks. Bartender Erich Berg is always ready with a quip. “I’m gonna give you a glass of water, hon. I like you,” he says to a thirsty customer.

Wondering what to order for a drink? Sidecar (what else?). The bar has no cocktail menu but specializes in the classics, like a strapping Manhattan or Erich Berg’s Old Fashioned, which can restore the sun on the gloomiest winter day. “Don’t threaten me with a good time!” he jokes. Cocktails are $10 to $13.