It's the talk of San Francisco: a temporary Cajun cafe

Ladling new meaning and spice into Hemingway's Parisian idiom ''movable feast ,'' chef Paul Prudhomme has fled steamy New Orleans this summer and taken his inimitable gumbos and crawfish pies on the road.

A few weeks ago, America's premier Cajun chef closed down K-Paul's Louisiana Kitchen, his world-famous French Quarter restaurant, and left a note on the door for his regular customers: ''Gone fishin' to Frisco.''

He moved his entire establishment - lock, stock, and Tabasco sauce - to San Francisco, where he is enjoying a 32-day run at the Old Waldorf, a defunct jazz club that in its heyday served forgettable guacamole and greasy hamburgers.

Mr. Prudhomme flew in herbs and spices, pots and whisks, as well as 20 of his best cooks, bakers, waitresses, and dishwashers, whom he is putting up for the month in the Victoria Hotel downtown.

Daily, the chef airfreights fresh catfish, softshell crabs, shrimps, and oysters from the Gulf coast, and nightly, San Franciscans make the pilgrimage to the impromptu restaurant on Battery Street, bringing lawn chairs, playing cards, portable televisions, even hors d'oeuvres, to endure the three- and four-hour queues.

It seems like a risky proposition. But Prudhomme, a man of collossal proportions and self-assurance, takes distinct pride in challenging America's time-honored, chicken-fried road-food tradition. He claims to be pioneering ''the traveling restaurant'' and trusts that the other great chefs of America will follow suit.

Although he can't leave home next year because of the World's Fair in New Orleans, he plans to take K-Paul's to New York in 1985. Paris is on the itinerary for 1986, and his waitresses are already taking French lessons.

''You used to be able to tell a good roadhouse restaurant by the number of trucks parked out front,'' said Prudhomme, slurping a cup of shrimp and okra gumbo in his makeshift kitchen. ''Now all it means is they have a big parking lot. We're trying to change that.''

The Cajun chef is enthroned on a wooden stool between the stove and refrigerator. Bundled in a white uniform and roadster cap with a ''TOTALLY HOT'' button on its rim, the bearded Prudhomme rested an outstretched hand on a silver-headed walking stick. From this corner the chef surveyed his realm and received fawning customers.

Paul Prudhomme, son of a Cajun sharecropper, is the youngest of 13 children. His mother taught him to cook when he was 7, and at 17 he started a drive-in in Opelousas, the central Louisiana farming town where he grew up. Nine months later, when the burger stand failed, Prudhomme hit the road.

He left the bayou country and apprenticed in kitchens from Chicago to San Francisco. Eventually he returned triumphant to Louisiana, where eight years ago he became ''corporate executive chef'' for Ella and Dick Brennan's well-known restaurant group in the South. At Commander's Palace, the Brennans' highfalutin flagship in New Orleans, Prudhomme collected well-earned kudos as America's most innovative Cajun chef.

The term Cajun, which refers to the cuisine and language of nearly a million people living in Louisiana's ''French Triangle,'' is a corruption of the word ''Acadian.'' Cajuns are the nation's largest French-speaking minority and are descendants of fisherfolk in the coastal provinces of Normandy and Brittany who migrated to Louisiana (via ''Acadia,'' a colony they founded in Nova Scotia) in the 18th century.

In the summer of 1979 Prudhomme and his wife, ''K,'' opened K-Paul's, a dark, unpretentious eatery on Chartres Street next to the brick ruins of an old police station. The ''dump,'' as Prudhomme describes his restaurant, serves beverages in pint and quart Mason jars and inscribes the chef's recipes on the ceiling inside cartoons of dancing barnyard and bayou critters featured on the menu.

All of Prudhomme's ingredients are fresh and seasonal. Rabbits, ducks, and ''yard'' hens are specially raised, most of the vegetables are organically grown , and the meats and sausages are home-cured and smoked.

Strangers crowd family-style around K-Paul's tables, where they dine on ''Cajun popcorn'' (deep-fried crayfish and crab meat) and redfish with czarina sauce. The food is as rich as Midas, but the decor and service are strictly no-frills. Spelled out at the bottom of the menu are K-Paul's ''rules'': ''No reservations, no credit cards, no checks, no substitutions.''

When you clean your plate, the waitress sticks a gold star on your forehead.

K-Paul's reputation has grown by word of mouth, and now there are lines down the block. For 50 select friends and loyal diners Prudhomme granted most-favored-customer status with a special card that gets them through the front door without waiting.

To thin out the hordes, he also opened K-Paul's Louisiana Grocery upstairs, where he serves plate lunches, Italian meatball ''poor boy'' sandwiches, and fried oyster loafs and markets his special Cajun ''magic seasoning.'' The grocery has remained open while Prudhomme has ''gone fishin' to Frisco.''

''Coming to San Francisco started off as a joke with my wife about putting a restaurant on a boat and going from port to port,'' said the bearded Prudhomme, leaning back against a shelf crammed with jars of bay leaves, black pepper, mustard seed, and bread crumbs. ''It's a crazy idea and I'm sticking my neck out , but . . .''

Prudhomme was interrupted by his wife and business partner (she's the ''K'' in K-Paul's) a trim and tidy redhead who entered the kitchen with a concerned look and a thick slice of the pecan butter cream cake.

''Too spicy, don't you think?'' she said, offering the chef a fork. Prudhomme took a bite. Then another, and another. He devoured the entire slice in silence, then proclaimed: ''As usual, her taste buds are right.''

By that time waitresses were returning to the kitchen with orders from the second sitting. To be heard above the rambunctious Cajun fiddle and accordion music in the dining room, Jan, Prudhomme's kitchen quarterback, barks out requests to the grill.

''Three triple tails and a rabbit.''

''One Pompano. One etoufee.''

''Two lamb - one medium, one medium rare.''

Prudhomme began jabbing his walking stick at a sous chef on his left. ''Watch what you're doing.'' Moments later he was showering fatherly concern on a young baker who had burned her hand.

''You all right, Dixie?''

Assured of her safety, he launched into his thumbnail history of Cajun food. ''It came from France with my ancestors 400 years ago.'' Cajun cooking was often based on necessity. It employed an assortment of exotic ingredients at which most Yankee chefs wouldn't shake a rolling pin: alligator, armadillo, catfish, crayfish, the ''bayou's best.''

Cajun cooking, said Prudhomme, is essentially French country cooking. When the Cajuns moved to Louisiana they borrowed wild sassafras, bay leaves, and thyme from the Indians and began cooking with a wide variety of hot peppers.

Like the language, Cajun and Creole cuisine is a melange. Among the most important contributors, Prudhomme said, were the black Creole cooks employed by the Spanish, Italian, French, Irish, and Anglo families living in New Orleans's posh Garden District. Through their sons and daughters, the domestics from Southern mansions handed down the amalgam of cooking styles now known as Creole cuisine.

''This gumbo is basically a southern France soup,'' Prudhomme said, sampling a mud-colored sauce from one of the stainless steel pots on the stove. ''Okra is frequently used in it. The African name for okra is gumbo. At K-Paul's we do nearly 20 kinds of gumbo.''

He cast a nostalgic gaze back toward the stove. ''Chicken and sausage gumbo is my favorite. The kind I serve here is exactly like my mother made when I was a kid in Louisiana.''

Why is Prudhomme's traveling restaurant debuting in San Francisco? ''There are three eating towns in America: New Orleans, New York, and San Francisco,'' Prudhomme said. ''We wanted to be a success our first time out, so we stacked the deck by coming to San Francisco. People here get emotional about food.''