Jack Czarnecki is a mycophile, an expert mycologist and a man who has turned mycophagy into an art. In other words, he is a man who not only loves mushrooms and is wise in their ways but who also can cook them to perfection.

As chef/proprietor of Joe's Restaurant, which boasts of being the only restaurant in the U.S. to specialize in cooking with wild mushrooms, and inheritor of generations of mushroom knowledge, he has been able to produce what is likely to become the definitive mushroom cookbook: "Joe's Book of Mushroom Cookery" (Atheneum, 1986; $20.95).

The new book is a natural for Czarnecki, whose family has been serving wild mushrooms in Reading, Pa., to local customers and food pilgrims from far-flung places since early in the century. Like the restaurant's menu, the recipes in the cookbook reflect Czarnecki's Polish heritage as well as "nouvelle cuisine" originality. Educated at the University of California at Davis, Czarnecki prefers light sauces and "California-style" combinations.

The restaurant is located in an unassuming area of downtown Reading, a place more commonly known for its outlet stores than for the mushroom industry, which also is important to the region's economy. Acclaimed by food luminaries such as Craig Clairborne, James Beard and Calvin Trillin, Joe's opened in 1916 as a working class saloon owned by Czarnecki's grandparents, Jozef and Magdalena. Polish immigrants, they enjoyed spending their Sundays in the nearby forests foraging for the wild fungi they remembered from home. During the week, they served a wild mushroom soup headier than the alcohol that was the mainstay of the business, and mushroom piroshki, two Polish dishes still on the menu.

When Czarnecki's father, also named Joe, took over, the establishment became more restauant than bar, until by the 1950s he had used his mushroom expertise and his culinary talents to turn Joe's into a mecca for mushroom fanciers. In a good year the restaurant may feature as many as 75 different types of mushrooms, and over the years the Czarneckis have served hundreds of varieties.

Since 1978 Jack Czarnecki, who gave up a budding career as a microbiologist to take over the restaurant after his father's heart attack, has put the stamp of his own cultivated taste and culinary creativity on the menu. He was called one of the six most innovative chefs in the U.S. by "Town and Country" magazine in 1982.

A friendly, balding man in his mid-30s, Czarnecki has perfected the art of cooking with wild mushrooms and prides himself on his understanding of flavor theory, which he learned at Davis and about which he gives lectures. Many mushrooms taste the same raw, he says, buttery and nutty, but cooked, each variety exhibits its unique characteristics.

He believes in the importance of imparting "roundness and fullness" to the mushroom's natural taste by adding the "three wise men" to a dish: salt for "palate responsiveness," soy sauce for "flavor expression" and sugar for "roundness and body." To bring out the natural flavors of cooked mushrooms, Czarnecki suggests adding butter, onions, garlic, sweet peppers, nuts, spices and herbs (especially savory, marjoram, thyme, sage and caraway seeds) and wine (only in sauces), and in his book he explains how each ingredient enhances the mushroom flavor.

He treats our domestic wild mushrooms with the same respect the French reserve for truffles. So most of the book's recipes are simple, prepared with a minimum of ingredients, in order to highlight the mushroom flavors. And, cooks are not required to truly forage for wild mushrooms, since the recipes call for morels, chanterelles, ce pes and the other woodland mushrooms that are becoming increasingly available in specialty food stores.

The book begins with chapters on buying and keeping mushrooms and on preparing such basics as mushroom duxelles, sauces, pure'es, stocks, extracts, butters, powders and liqueurs begin the book. Czarnecki includes the recipe for his mother's renowned wild mushroom soup, which is now marketed frozen, and for a domestic cream of mushroom soup that is nothing like Campbell's.

Dishes for light lunch or brunch include mushroom quiches, mushrooms with eggs or spread on croissants, mushroom fritters and souffle's, even mushroom tacos and mushroom hamburgers. As a first course, the book suggests, serve mushroom canape's, pate' or quenelles, or mushrooms saute'ed, braised, in cream sauce, fried, grilled, stuffed and pickled.

Then there are recipes for preparing mushrooms with fish, poultry, meat, furred game, pasta, grains and vegetables. Mercifully, there are no dessert recipes calling for mushrooms, only mushroom-shaped meringue cookies and other desserts served in the restaurant. They are the specialties of Czarnecki's German wife, Heidi, who learned them from her mother-in-law, Wanda.

There is one short chapter titled "Very Wild Mushrooms" for people who pick their own. Unless you are an expert, eating mushrooms you pick yourself is a bit like eating fugu, the Japanese blowfish sushi, which is delicious and perfectly safe when properly prepared by trained chefs but which carries the risk of death if the chef makes a mistake.

Czarnecki points out that while most wild mushrooms are safe, "a number of poisonous mushrooms actually resemble some very good and edible types and are often mistaken for them." To complicate matters further, toxic varieties grow "in large quantities" and some, such as those in the Amanita genus, are deadly. Czarnecki takes great pains to warn amateur mushroom hunters of the hazards. The book opens with a "special word of caution" and ends by admonishing, "This is not a sport for beginners."

He suggests that people interested in gathering wild mushrooms read books about them, join a mushroom-hunters' club and go out only with very experienced foragers who can make positive identifications. In this area, contact Frances Usenik (2327 49th St., NW, Washington, D.C. 20007, phone (202) 333-9350), treasurer of the Mycological Association of Washington.

JOE'S QUICK WILD MUSHROOM SOUP (4 servings)

At the restaurant, a more involved version of this hearty soup is served with a signature mushroom cap traced on the top with cre me fra" che.

1 ounce dried ce pes, washed

3 cups water

1/2 cup chopped onions

2 tablespoons melted butter

1/2 cup rich beef stock or equivalent from bouillon cube

1 teaspoon salt

1 teaspoon sugar

1 tablespoon soy sauce

1/2 cup flour mixed with 1/2 cup water

Bring mushrooms to a boil in the 3 cups of water and simmer 20 minutes. Save the water, slice the mushrooms and rinse them with fresh water. Place the mushrooms and the liquid from the reconstitution in a food processor. Add onions, butter, stock, salt, sugar and soy sauce and blend to a pure'e. Strain if lumpy. Bring to a boil in a saucepan. Stir constantly and slowly pour enough of the flour mixture through a sieve into the soup until it reaches the desired thickness.

BRAISED MUSHROOMS (4 servings)

This recipe is good with domestic or wild mushrooms. Use as a side dish or, if the mushrooms are special, as an entree served in pastry shells or puff pastry.

4 tablespoons melted butter

1/2 cup chopped onions or scallions

1/2 cup veal or poultry stock

8 ounces fresh mushrooms, sliced or whole

1 teaspoon salt

1 teaspoon sugar

1 tablespoon soy sauce

1 teaspoon dried savory or 1 tablespoon fresh

2 tablespoons cornstarch mixed with 1/3 cup water

In a saucepan melt butter over low heat. Add onions and saute' over medium heat until almost transparent. Douse them with water or stock and bring to a simmer. Add mushrooms and cover tightly. Simmer 1/2 hour over low heat. Mushrooms will be greatly reduced in size. Add salt, sugar and soy sauce and stir. Simmer 5 minutes and add savory. Mixture can be thickened and used immediately or frozen at this point. When ready to use, defrost and thicken with cornstarch mixture a little bit at a time.

PIROSHKI (Makes 24)

This recipe, originally Czarnecki's grandmother's, can be made with button mushrooms, fresh woodland mushrooms or dried wild mushrooms (soaked and chopped). The dough can be refrigerated for a week.

FOR THE DOUGH:

1 1/2 cups flour

1/2 cup (1 stick) very cold butter

3 tablespoons sour cream

FOR THE FILLING:

1/2 pound fresh button or woodland mushrooms

6 tablespoons butter

1 large onion, chopped

Pinch savory

Salt and pepper to taste

To make dough, sift flour into a mixing bowl. Slice butter into flour and cut it in with a pastry blender or fork until mixture resembles coarse crumbs. Add sour cream, tossing lightly with a fork just until mixture holds together enough to form a ball. Wrap ball in waxed paper or plastic and chill thoroughly, about 3 hours.

To make filling, clean and chop mushrooms fine. Heat 3 tablespoons of butter in a skillet and saute' mushrooms until they are dry. Transfer to a bowl. Heat remaining butter and saute' onion until golden. Add to mushrooms. Mix well and season with savory, salt and pepper. Chill 1 hour.

To assemble, begin by pinching off a scant tablespoon of dough and roll out on a lightly floured surface to a circle 3 inches in diameter. Trim edges with a pastry wheel or cut with a 3-inch cookie cutter. Repeat until all dough has been used. Paint edges of circles with a little water. Put 1 teaspoon filling in center of each circle. Fold over to make small turnovers, pressing edges together with the tine of a fork. Pierce tops with the tines of a fork. Place on an ungreased baking sheet and chill 1 hour. Bake in a 400-degree oven 15 to 20 minutes or until golden brown. Serve immediately.

VENISON AND SHIITAKE CASSEROLE (4 servings)

This is a signature dish at Joe's, made with Scotch roebuck. Czarnecki says, "The rich, sweet taste of hoisin is a natural complement to the gaminess of the roebuck and consistent with the philosophy of venison cookery of Middle Europe. Serve with kasha (buckwheat groats)."

2 pounds venison, boned and cut in 1/2-inch pieces

3 cups red wine

2 cups water or veal stock

2 cloves crushed garlic

1/2 cup chopped onions

1 teaspoon salt

2 tablespoons hoisin sauce

Salt to taste

16 medium caps fresh shiitake mushrooms

2 tablespoons arrowroot mixed with 1/3 cup water

In a saucepan combine venison, wine, water or stock, 1 clove of garlic, onions, salt and 1 tablespoon hoisin. Bring to a boil, cover and simmer until venison is tender, about 1 1/2 to 2 hours. Remove meat and transfer liquid to a clean saucepan.ld,10.8 Add remaining garlic and hoisin, bring to a boil and reduce by 1/3. Salt to taste. Add shiitake and venison, bring to a boil and simmer 5 minutes. Thicken with arrowroot mixture.

SOFT-SHELL CRABS WITH CHANTERELLES (4 servings)

Czarnecki calls this simple recipe "devastatingly delicious," and it is just in time for soft-shell crab season.

8 soft-shell crabs, cleaned

Flour for dredging

Salt to taste

2/3 cup melted butter

1/3 cup fresh lemon juice

2 cups sliced fresh chanterelles

Coat crabs with lightly salted flour. Combine butter and lemon juice and add 1/4 of it to a nonstick skillet. Add chanterelles and saute' 2 minutes. Remove and keep warm. Leave remaining liquid in pan. Saute' crabs, 2 at a time, in mixture, adding lemon butter as needed. Saute' 3 minutes on each side. Remove and keep warm until all crabs are cooked. Return chanterelles to pan, stir and pour over crabs.

CHICKEN WITH OYSTER MUSHROOMS (4 servings)

*1 1/2 cups whipping cream

1/2 cup chicken stock

1 tablespoon cream sherry

1 teaspoon crushed garlic

1 tablespoon prosciutto or westphalian ham, chopped fine

12 ounces cooked chicken breast, cut in 2-inch strips

8 ounces fresh oyster mushrooms, sliced into 2-inch strips

Salt and pepper to taste

2 tablespoons cornstarch mixed with 1/3 cup water

Combine cream, stock, sherry, garlic, ham, chicken, mushrooms, salt and pepper in a heavy skillet. Heat over medium heat until simmering. Reduce heat to low and simmer 5 minutes. Thicken with cornstarch mixture.

SCRAMBLED EGGS WITH MORELS (4 servings)

"This delightful and distinctive dish," says Czarnecki, "is best with fresh morels. Dried morels can be used, however, since the flavor of the green pepper will support the flavor of the morels very effectively."

1/2 tablespoon minced onion

1/2 tablespoon minced green pepper

1 1/2 tablespoons melted butter

1/2 cup fresh morels, sliced, or 1/3 cup dried morels, reconstituted

1/8 teaspoon salt

1/8 teaspoon sugar

1/2 teaspoon soy sauce

8 eggs

Saute' onion and green pepper in melted butter until onion is transparent. Add morels and saute' 1 minute. Add salt, sugar and soy sauce and continue to cook until mixture has given up most of its liquid.

Lightly beat eggs and add to mixture. Cook until eggs are done to taste.

Serve with bagels or croissants.