At the Cajun Yankee in Boston, the phone rings constantly, but owner-chef John Silberman can spare only an hour a day to take reservations. The place is booked solid three weeks in advance by patrons eager for unlikely Beantown dishes like scrod sautéed in Louisiana pecan sauce and baked chicken stuffed with oysters from the local waters. At Philander's Oak Park in Illinois, chef Frank Chlumsky can't keep enough Gulf Coast redfish on ice. And at Orleans, the newest Los Angeles Cajun eatery, Barry Manilow, John Lithgow, Morgan Fairchild and Bette Midler are among the celebs who have blissfully abandoned avocados and nachos for Cajun popcorn (deep-fried crawfish morsels) and fettuccini with oysters.

The new Cajun chic began with K-Paul's Louisiana Kitchen, an unpretentious café that Paul Prudhomme, 44, and his wife, Kay Hinrichs, 40, opened in New Orleans' French Quarter in 1979. K-Paul's rich, piquant food attracted a devoted following, and soon lines stretched around the block. Capitalizing on Prudhomme's success, Cajun restaurants began proliferating about as fast as crawfish at spawning time. There are at least a dozen in New York, four in Washington, three in Chicago, four in L.A. and others sprinkled around the U.S.—an encouraging number, say restaurateurs, for a taste as specific and sophisticated as Cajun. Those who aren't dining out on these spicy delicacies seem to be cooking them at home: Chef Paul Prudhomme's Louisiana Kitchen (William Morrow, $19.95), with nearly 300,000 copies in print, was on the New York Times best-seller list for 13 weeks, extraordinary for a cookbook that doesn't have the names Julia Child or Fanny Farmer in the title.

Why the sudden hot spell? "When you've gone through your sushi phase and your salad phase, you get bored," explains L.A.'s Jake Ptasznik, owner of Orleans. "Then you start looking for something exciting to sink your teeth into." Sam Duvall, an owner of L.A.'s Ritz Cafe, another celeb hangout, thinks folks have finally found a stomach for "gut food." Then, too, the Louisiana World Exposition generated new interest in New Orleans and its savory charms.

Prudhomme, a 400-pounder who weighed 500 pounds when he was 15, does not blame his girth on the calories in Cajun. "You can be thin and be a great cook," he says. "I don't know what keeps me fat." But while he relishes his native cuisine, he also frets about the future. "My nightmare is that there are going to be drive-up windows with Cajun food," he says. In fact, there probably will never be a McCajun, since the recipes call for a subtle blend of fresh ingredients, complex seasonings and long, slow simmerings.

As Prudhomme explains it, Louisiana cuisine is a mix of two styles. Cajun is country cooking, brought to the Louisiana bayous by French settlers called Acadians (hence "Cajuns"), who were driven from Nova Scotia by the British in the 1700s. They used native spices—filé powder from the sassafras tree, bay leaves from the laurel, wild peppers—to flavor the bountiful fish and game. Creole is city food, a sophisticated New Orleans mélange of French, Spanish, Italian, African and American Indian cuisines handed down over the generations. Prudhomme's crawfish smothered in a dark sauce, called an etouffée, is Cajun, his mirliton (a member of the cucumber family) stuffed with fried oysters and topped with hollandaise sauce is Creole. "That's one of those kick-you-in-the-pants dishes, boy, I'll tell ya," boasts Prudhomme. "It has so many tastes, and every bite whops up on something else." His most famous dish, blackened redfish, a filet charred and smoked in a white-hot iron skillet, is, however, an original.

So is the jovial chef. A folk hero in Louisiana, Prudhomme has had his own television show for 12 years and is a regular guest on a New Orleans morning talk show. He was picked to head the state's delegation to last January's Inaugural. After a bash where he and his staff fed 32 different dishes (including oyster and brie pie and chicken smothered in black-eyed peas) to 990 Reaganites, he stepped out to shake hands with the President.

The White House is a long way from the Louisiana swamps near Opelousas, where Prudhomme grew up as the 13th and youngest child of sharecroppers. At 17, he opened a hamburger stand—which failed—then toiled as a busboy, cook and magazine salesman in New Orleans. Later, heading West, he cooked at truck stops and resorts for 12 years before returning home. In 1980 he left a high-salaried job as an executive chef and joined Kay in the running of K-Paul's.

Anxious to spread the gumbo gospel, Prudhomme dreams about opening a chef's school on a 100-year-old sugar plantation outside New Orleans. "Cajun makes you happy," he says. "It's emotional. You can't eat a plate of Cajun food and not have good thoughts."