Henry Chung has survived the uncertainty of exile from his native land and the pressure of having his tiny family place, the Hunan, cited by The New Yorker as th finest Chinese restaurant in the United States. Modesty, dignity and calm intact, he is about to take a quantum leap. This month he has opened a second Hunan, which, with 314 seats, is 10 times the size of his present restaurant.

He also survived a private dinner recently, attended by the gastronomic elite of the city along with a surprise guest - entertainer Danny Kaye, who is unchallenged as the best non-Chinese Chinese cook in the United States.

Chung's triumph is all the more remarkable because he was in his 50s, pursing a career as an office worker, before he decided to become a restaurateur. The place he opened, a storefront at 853 Kearny St., has six tables and 11 counter seats. It lacks elegance and it lacks space. You might walk right by without noticing, as you do countless others in crowded Chinatown. What sets it apart is the standard of cooking enforced by Chung, the novelty of food prepared in the authentic Hunan manner and the liner outside waiting for a seat.

Hunan province, best known to some as the birthplace of Chairman Mao, has a rich and varied cuisine, the capstone of which is not pepper. They are not the fragrant peppercorns of Szechuan nor Mexican chile peppers ("too sweet," says Henry Chung). Green when fresh, red if dried, they are small and "nippy," a piece of Chinese understatement meaning they can blow off the top of your head.

"Hunan people can live without meat," Henry Chung claims, "but they cannot live without hot pepper."

Somehow Americans have gotten the message. For several years now they have been flocking to restaurants featuring spicy Szechuan food. Hunan - more varied and sophisticated but less well known - has begun to catch on, too. Chung was the first to raise the banner of Hunan in this city's largely Cantonese Chinatown in 1974.

Loni Kuhn, a widely respected cooking teacher here, lined up on the first day and has been back regularly ever since. "Every week or so, I need a Hunan fix," she said. "It's gotten to the point where I really don't like any other Chinese food. The other styles seem so terribly dull."

San Franciscans of Cantonese descent don't share her view. Regional culinary arguments in China are no less passionate than those among chilliheads or barbecue fanciers and detractors in this country. So Henry Chung's voice is tinged with a touch of pity as he says, "Cantonese don't like spicy, hot food. Most Chinese come here to eat noodles." According to Chung, the proprietor of a luxury Cantonese restaurant on Grant Avenue reacted to the critical acclaim heaped on the Hunan with scorn, saying, "That little place is just for working people."

Danny Kaye, who has a scholar's knowledge of Chinese culinary lore, tried to put the debate in perspective. "There's a difference between spices stimulating the taste buds and paralyzing them," he said. "A truly fine Chinese meal will be orchestrated like a symphony to provide harmonies of texture, color and seasoning."

All this sophistry bothers Henry Chung not one whit. He nods politely, then continues to do just what he has been doing. To a Frenchman, the argument would boil down to choosing between the haute cuisine refinements of a Parisian palace of gastronomy and the rich provincial fare of the countryside surrounding Lyon.

Like the Lyon area in France, Hunan has the best assemblage of natural foodstuffs in China. As Tony Hiss writes in his introduction to "Henry Chung's Hunan Style Chinese Cookbook" (Harmony Books, $10). Hunan "is the only province in China whose people have always had three square meals a day, with plenty of rice, vegetables, pork or chicken, and fish at most meals."

(The book contains about 75 surprisingly uncomplicated, well explained recipes, a succinct introduction that will serve as a valuable primer to all Chinese cooking, and fascinating and amusing tales of Hunan. Like the restaurant, it's a winner.)

"Our food is very unusual," Chung said. "It is more than just hot and spicy." He, and others, can cite magnificent smoked poultry and pork recipes, exquisite dishes that would be too highly sugared without the counterpoint sparks struck by hot pepper, and a simple onion cake - essentially a scallion-flavored tortilla - that is as addictive as potato chips.

"There are three explanations as to why they (the Hunanese) like hot and spicy food so much," Chung writes in his book. "One has it that hot pepper and spices are used instead of salt because Hunan is far from the salt-producing areas . . . The second is that, because of their hot and humid climate, the Hunanese people eat hot pepper and spices to promote perspiration. And the third says that because Hunan abounds with food, Hunan people try to eat more than they otherwise could by adding hot pepper and spices to stimulate the dull appetite.

"There is more or less truth in each of the explanations, and evidence especially to support the third belief. . . "

The menu he planned for the private party (on Sunday, a day when the restaurant usually closes) emphasized both quantity and hot peppers, though Chung acknowledged he hadn't pulled out all the stops. On a blackboard he had listed: Hunan-Style Hot and Sour Soup Onion Cakes Five-Spiced Beef (cold) Fried Chicken Wings Chicken Salad Hot and Sour Beef Rock Cod with Hot Black Beans Hot Spiced Shrimp Chicken with Garlic Sauce Bean Curd with Meat Sauce Henry's Hunan Smoked Tea Duck

It is necessary to resort to that overworked phrase "utterly without pretense" to provide a framework for the food and the evening.

The guests drank beer or cola from tea mugs. The napkins were paper. Danny Kaye and several others perched on stools at the counter. Others sat at uncovered formica tables. There was no order of courses and no drum rolls when a new dish appeared. Chung's wife, Diana, and two women helpers worked at the four-burner stove and two woks behind the counter short-order style. (There is no kitchen. At the Hunan, what you see is what you get.) Chung and his son would deliver the platters. People talked and walked. Guests and hosts mixed and mingled at will.

The duck was marvelous, lean and musky. The white, soft, bland bean curd and the chunky, fiery meat were an ultimate yin and yang combination. The "chicken salad" title is somewhat misleading. This particular combination never has been served at a picnic or church social. Noodles, cucumber and shredded chicken are swathed in a sauce with an eye-popping array of peppery nuances. (The recipe has been appended to this article.)

Not everything was spicy hot. The chicken wings were crisp and fresh, the chicken with garlic sauce was more fragrant than fearsome and after the tear-jerking taste of hot spiced shrimp, more onion cakes appeared to sooth the palate.

Was it the best food? Is it the best restaurant?

Those determinations can't be made objectively. What can be said is that at the Hunan the ingredients are first rate, the cooking is as distinctive as one would hope, the prices are less than they need be and the host is a man of great good will and touching sincerity.

Henry Chung is planning a Hunan museum for the second floor of his new restaurant (at 924 Sansome St.). "Someday before I kick the bucket," he said, "I want to give it to the city. I came here in 1948 with nothing. My kids were educated by scholarship. I owe so much to the people of this country. So I want to do my part."

That he is not, as he put it, "after greenbacks" is apparent from his prices. "It's not like opening a jewelry shop," Chung said. "Everybody has to eat and I want everybody to be able to buy my food.

"I never keep anything secret," he said of his cooking. "You can come and watch me. The ingredients, equipment and (health) inspection we have here are better than in China. I think we even have better food."

Customers come from all over nowadays. Chung claims "it doesn't matter. I just do my work. But the more publicity, the more frightened I am. If people come and are disappointed, that is the cruelest thing I could do.I don't want to fail them."

Why, then, take on the challenge of the new, larger restaurant a few blocks away that he and his son will operate while his wife stays behind to manage the "foundainhead"?

"Because," Henry Chung said, "I like to see more people with smiling faces." CHICKEN AND CUCUMBER SALAD 1 ounce dry agar-agar, cut into 1-inch-long pieces (or 1 ounces vermicelli, Chinese bean noodle, or bean noodle sheet) 1 to 2 cups finely shredded cucumber (use fresh, green, firm cucumbers) 1 1/2 to 2 cups cooked and finely shredded chicken meat (shred by hand) 1 1/2 cups rich hot and sour salad dressing (approximately) (see below) 1 tablespoon sesame oil (optional) 1 tablespoon minced scallions (optional)

Soak the agar in warm water for 15 to 20 minutes. (If you're using bean noodle or bean noodle sheet instead, soak it in warm water for 20 minutes, then cook it in boiling water for 3 to 5 minutes. Remove it and rinse in cold water.)

Squeeze the agar-agar or bean noodle dry and place it in a bowl.

Spread the shredded cucumber over the agar-agar; then place the shredded chicken on top of the cucumber.

Pour salad dressing over the chicken, and garnish with sesame oil and scallions if desired. Mix well before serving. RICH AND HOT SOUR DRESSING 2 tablespoons sesame seed paste (or crunchy-style peanut butter) 2 tablespoons soy sauce (or to taste) 4 tablespoons vinegar (or to taste) 1 tablespoon hot red pepper oil 1 teaspoon hot red pepper powder 1/2 teaspoon black pepper 1 teaspoon sugar (optional) 1 tablespoon sesame oil 2 tablespoons vegetable oil 1 tablespoon finely minced fresh ginger 1 tablespoon finely minced garlic 1 tablespoon finely minced scallions 1 tablespoon white wine 1 tablespoon hot mustard (optional) 1/2 teaspoon salt 1 to 2 cups chicken broth

Mix all above condiments together. POACHED FISH FILLETS IN SOUR SAUCE 1 1/2 to 2 pounds fillet of sole or other mild whitefish 2 tablespoons minced scallions 1 tablespoon finely shredded fresh ginger 1 teaspoon black pepper 2 to 3 tablespoons vegetable oil 2 cups chicken broth 3 tablespoons soy sauce 1 tablespoon sweet peas 2 tablespoons white wine 1/2 teaspoon sugar (optional) 2 tablespoons vinegar Pinch salt 1 tablespoon liquid cornstarch (1/2 tablespoon powdered cornstarch mixed with water) 1 tablespoon sesame oil

Add 8 to 10 cups water to a wok. Bring to a boil. Poach the fish for about 2 minutes (do not overcook it). Remove the fish to a serving dish. Pour water from wok. Sprinkle scallions, ginger, and black pepper over the fish.

Heat 2 to 3 tablespoons vegetable oil in the wok until smoking hot. Pour oil over the fish.

Clean the wok; add chicken broth; bring to a boil. Add soy sauce, sweet peas, wine, sugar, vinegar, salt (but taste the sauce before adding any salt), and liquid cornstarch; stir lightly until the sauce thickens and clears (about 10 seconds). Pour the sauce over the fish, garnish with sesame oil, and serve hot.

Variations: For hot and sour fish, add 1 teaspoon hot red pepper powder or 1 teaspoon hot pepper oil to the sauce when you add soy sauce. For sweet and sour fish, add 1 to 2 tablespoons sugar at the same point. SPICED EGGPLANT IN HOT (AND MEAT) SAUCE 1 American eggplant (or 4 to 5 oriental eggplants) 4 tablespoons vegetable oil 1/2 cup finely minced pork, with fat left on 1/2 tablespoon minced fresh ginger 1 tablespoon minced fresh garlic 1 1/2 tablespoons Szechuan hot bean sauce 1/2 tablespoon minced pickled hot pepper 2 tablespoons soy sauce 1/4 cup chicken broth 1 to 2 dashes black pepper 1/2 tablespoon vinegar 2 tablespoons minced scallions Dash salt 1 tablespoon sesame oil 1 tablespoon chopped parsley

Cut the eggplant into 1/2-inch-thick slices 2 inches long; American eggplant should be peeled, but not oriental.

Heat a wok over highest heat for 1 minute; then add vegetable oil. As soon as the oil is smoking hot, fry the minced pork until it begins to change color, then remove pork with a slotted spoon and set aside.

Reheat the oil until smoking hot. Add ginger, garlic and eggplant slices, stir-fry and mash over medium heat until the eggplant slices become thoroughly soft.

Add hot bean sauce, minced pork, pickled hot pepper, soy sauce and chicken broth, stirring over high heat for 1 minute more.

Add black pepper, vinegar, scallions, and salt (to taste.) Stir until thoroughly hot and blended. Serve at once, garnished with sesame oil and parsley. Some people may think this dish is a little oily, but it is delicious.