"I'll have the sole," the young man says matter-of-factly to the waiter, "because it looked bad."

It's all in a day's work for restaurant Jason Wolin, head of a growing family fiefdom begun in Washington a couple of years ago when he turned an empty Georgetown gas station into a trendy hot dog palace. Today Wolin, along with his younger brother and mother, is opening eateries at the rate of one every six months. And on this particular day, Jason Wolin is sampling the sole at the family's chic Capitol Hill restaurant, 209 1/2, to make sure the fish is up to snuff.

"You can't play around," he says with a professional briskness that belies his age, which is 25. (Brother Joel is 23, and Mom, Rochelle Rose, "isn't talking.") "This is a city of international eaters. They know . We opted for four things on the menu at lunch and three at dinner, and they're changed every month. . .Oddly, the goal was to keep the staff on its toes, to keep inventory moving." But Jason says the revolving, limited menu also served to keep the public interested. Customers and dining reviewers so far have agreed with him.

During a Chicago boyhood, as he watched his mother prepare elaborate dishes for parties, Jason Wolin had ambitions.

Recalls Rochelle Rose: "He'd say, 'You know, mother, we could really open up a restaurant.' He wanted to sell pies. He said we could get a deposit on the pans. . .Who would have thought?"

For that matter, who would have thought a 23-year-old could make money with a place called Hot Diggity Dog? In Georgetown. As an international relations major at American University, Jason worked at Clyde's, dreaming of a restaurant of his own.

"One day Jason called me in Chicago," his mother says, "and said, 'Listen, I want a restaurant, and I want it now.'"

Hot Diggity Dog opened along with the nation's Bicentennial.The Wolins (Mom arrived to help, as did Joel, then a college student managing a McDonald's) served nitrite-free, all-beef hot dogs, some embellished with cheese, tomatoes, dressing, chile and saurkraut. They had a hit. National media attention accompanied the success of the snappy place that sold the humble American staple, the hot dog.

The Wolins were selected to operate the cafeteria at the National Portrait Gallery, a place that impressed a Supreme Court justice enough that the Wolins eventually took over the operation at the high court from a large company. About a year ago, the Wolins sold Hot Diggity Dog (because a buyer offered a handsome price, Jason said), and Jason's brother and mother settled in Washington permanently.

Jason acts as company comptroller and plots new projects. Joel handles logistics, visiting each of the family's three establishments daily, beginning at about 5 a.m. Jason is on the telephone by 6 a.m. checking on the previous day's receipts. Rochelle sleeps in, beginning work at about 10 a.m. at 209 1/2. The family "reads cookbooks like novels," says Rochelle, who counts 1,000 cookbooks on the shelves. All three Wolins are workaholics, with Jason as ringleader.

"When some people go home they do crossword puzzles," Joel says. "Jason writes menus and draws facades for new restaurants."

"He's so organized," says Rochelle, watching her middle son (the oldest is a TV newsman in Florida) write neat notes on a legal pad as he eats lunch. "I always said Jason even files the garbage."

Jason picks at the sole, which turned out to taste better than he had expected. But he's not delighted with the dish as a whole.

"This could be replaced," he says. "It's a little too B. Altman.Like something you'd get at the Birdcage at Lord & Taylor.But ladies on a diet, they'll like it."

The sole entree, ther, weighed carefully on a palate to which hot dogs are only history, lives another day.

Footnote: Next Wolin project will be an intimate restaurant in Foggy Bottom to be called Martha's Vineyard, with a changing American-New England menu. And the biggest gamble, but potentially the most interesting project, will be a fifth eatery, Cafe du Marche, that will serve food from midnight to the afternoon. To be located in an as-yet-unidentified wholesale produce market, the place will try to recreate the restaurants that clustered near the late, great Parisian produce market, Les Halles. Except the Wolin version will feature a phone at every table so business can be conducted through the morning hours.