With demands for changes in diet focusing on lessened intake of sugar, butter, eggs and cream, one might think the pastry chefs of the world are facing extinction and have volunteered for retraining at the fish or vegetable station. That's not the case, according to a leading member of their band.

Albert Jorant, a pastry cook for nearly 50 years, responded with a patented Gallic shrug when asked if the French were giving up their beloved pastries in the face of diet warnings and publicity surrounding low-calorie cuisine minceur. "Not at all," he said. "The proper way is to eat desserts but in moderation."

Jorant teaches the making of pastry at La Varenne, a new cooking school in Paris that has been attracting a large number of students from the United States. He was here last week to do a demonstration at L'Academie de Cuisine in Bethesda where a packed house of attentive students were evidence that the pastry underground is alive and well organized. Joran speaks no English, so Francois Dionot, the Academie's resident professor of cooking, acted as translator and assistant during the two-hour session.

Both are antagonistic to cuisine minceur . "You can't take away cream and butter and expect to do French cooking," Dionot said. "What else would you put in?" responded the man from Paris.

Jorant went on to explain that while it was possible to reduce the quantities of sugar in some instances, the formulas for puff pastry, meringue and other baked items depended for their success on a balance among ingredients. Instead he advocates reduced portions and isn't opposed to substitution of sherbet or fresh fruit by those who have used up most of their calorie allotment when the time for dessert comes around.

Earlier his desserts had passed the taste test with flying colors and in so doing underscored a premise gastronomes have long aruged: It is possible to be satisfied with less, if that less is truly satisfying. A couple of bites of buttercream sandwiched between layers of meringue were heady stuff; rich, full of flavor and leaving sensations behind to chew over in the memory. Heavily sugared food that is bland and boring, the argument goes, is gobbled down precisely because it does not truly satisfy the person eating it. The person eats on in search of something he or she will never find in Twinkies or some similar mass-produced pastry confection.

A man of humor and extraordinary technical deftness, Jorant passed out trips as he worked and after the demonstration offered some evaluations of American products used in pastry-making.

He rated American butter as "zero," said sugars were about the same, salt was less salty here and, to Dionot's surprise, had no complaints about the chemically rich whipping cream sold in supermarkets. Our all-purpose flour was "often too compact, colors less well and needs a higher temperature for cooking." Dionot suggested one reason for the difference is that flour here has been in bags much longer before it is used and therefore is drier. Jorant raised a few eyebrows by suggesting one mix all-purpose flour half and half with so-called instant flour to lighten it before baking.

He counseled the students to value quality ingredients and know their ovens before all else. Precision in the beginning steps is all important, he said. Variation and fantasy have their place in flavoring and decoration once the baking is done.

Among the "tricks" he revealed: He used chilled flour along with chilled eggs and butter to make a tart crust, and does so for any pastry that does not require the addition of yeast and heated ingredients. He chilled a marble slab with ice cubes in a plastic bag, then made the dough and formed it into a crust directly, without placing it in the refrigeration to "rest."

He advised adding a small amount of salf to any sweet pastry and separating eggs cold to avoid breaking yolks.

He demonstrated shaving and curling chocolate with a potato peeler, mixing (as opposed to beating or folding) with a controlled movement involving only the wrist while turning the bowl with the other hand. He loosened meringue stuck to paper by pouring a small amount of water into the still-hot pan and replacing the paper. (The meringue sticks because too high heat cooks some of the sugar separately. It comes away from the paper because a small amount of steam is formed.)

Joran made a lemon tarte, an oblong meringue dessert called a gateau progres and a round meringue dessert called a sucess . Along the way he created praline, buttercream and pastry fish.

Recipes from La Varenne follow, along with one of the prize recipes from a book that should be in hte library of every home cook who makes desserts, whether or not he or she eats them. The book is "Maida Heatter's Book of Great Desserts" (Knopf, $10). LA VARENNE'S GATEAU PROGRES

(10 to 12 servings) 3/4 cup shelled hazelnuts 3/4 cup whole, blanched almonds 2 cups sugar 8 egg whites 1/2 teaspoon vanilla For filling: 4 egg yolks 1/2 cup sugar 1 1/2 cups unsalted butter 1/2 cup whole, unblanced almonds 1/2 cup slivered almonds, browned and chopped Confectioners' sugar

Toast hazelnuts and whole, blanched almonds in a 350-degree oven until browned, 8 to 12 minutes. Let cool slightly, then rub hazelnuts with a rough cloth to remove skins. Grind nuts to a powder, a little at a time in a blender, food processor or rotary cheese grater.

Grease and flour two baking sheets and mark three 9-inch circles with a pan lid. Preheat oven or ovens to 325 degrees.

Prepare the meringue layers by stiffly whipping the egg whites. Beat in 2 tablespoons from 1 cup of sugar for 30 seconds until whites are glossy, then fold in remaining sugar from the cup. Fold in ground nuts and vanilla. Spread or pipe the mixture through a pastry tube (Joran used a No. 5 plain nozzle) to fill the circles on the baking sheets. Bake until meringues are lightly browned, 12 to 15 minutes, moving sheets as necessary to insure even baking. Trim rounds neatly with a sharp knife while still hot, then transfer them to a rack to cool.

Next make praline by cooking the unblanched, whole almongs in 1/2-cup sugar without liquid. The pan should be heavy-bottomed. As the sugar melts and then caramelizes, the heat will toast the nuts. Stir from time to time and don't allow the sugar to burn. Turn out immediately onto an oiled baking sheet (or marble slab). When the mixture has cooled, grind it, a little at a time, in a blender or rotary cheese grater. (Do not put unground mixture into a food processor; the hard sugar may scratch the bowl.)

Heat 1/2 cup sugar with 1/2 cup water to 220 degrees or soft-ball stage. Using an electric mixer, slowly pour syrup into beaten yolks. When all syrup is incorporated and mixture has cooled, mix in the unsalted butter. Beat in the powdered praline.

Assemble the cake by spreading about a third of the buttercream frosting on two layers. Place one atop the other, add the third and cover the top and sides with remaining frosting. Sprinkle the top thickly with confectioners' sugar and press chopped almonds about the sides with a metal spatula.

This cake will keep in the refrigerator for two or three days.

LA VARENNE'S LEMON TARTE

(6 to 8 servings) For the pastry: 1 1/2 cups flour 1/4 teaspoon salt 1/2 cup butter 3 eggs yolks 1/3 cup sugar 1/2 teaspoon vanilla For the filling: 3 eggs 1/2 cup sugar 2 lemons, juice and grated rinds 3/4 cup whole, blanched almonds, ground 3/4 cup melted butter

Make the pastry by sifting flour with salt onto a board and forming it in a circle with a well in the center. Place butter, yolks, sugar and vanilla in the center and work with the fingertrips of one hand to make a smooth mixture. Using the fingers and heel of the hand in a rocking motion, gradually work in the flour. Gather up flour from the outside with a knife held in the other hand. When the dough is smooth, lightly flour the board and work the dough into a ball. With the heel of the hand, push dough away from the mass and incorporate it again, working until it is pliable. (This may be done without kneading in a food processor.)

Wrap dough in plastic warp and chill for 30 minutes. Preheat oven to 375 degrees.

Grease a 9-or 10-inch pie pan or flan ring, roll out the pastry dough and line the pan. Place pan in refrigerator. Make the filling by beating eggs and sugar until the mixture leaves a ribbon trail when lifted.Stir in lemon juice and rind, then the melted butter and ground almonds. Place pie shell atop a baking sheet and pour in filling. Bake in bottom third of oven until filling is golden brown and set, 30 to 40 minutes. Cool to room temperature before serving. This tarte may be made six to eight hours ahead of serving, but is best served the day it is made. MAIDA HEATER'S QUEEN MOTHER'S CAKE

(12 serving) For the cake: Fine, dry bread crumbs 6 ounces sweet or semisweet chocolate, coarsley cut or broken 6 ounces (3/4 cup) butter 3/4 cup sugar 6 eggs, separated 6 ounces (1 3/4 cups) almonds, finely ground 1/3 teaspoon salt For the icing; 1/2 cup heavy cream 2 teaspoons instant coffee 8 ounces sweet or semisweet chocolate, coarsely cut or broken

Ajust rack one-third up from bottom of oven. Preheaat to 375 degrees. Butter a 9-by-2 1/2-or 3-inch springform pan and line the bottom with wax paper or baking pan liner paper. Butter the paper and dust all over it lightly with fine, dry bread curumbs.

Melt chocolate in a small double boiler over hot water on low heat. Remove from heat and set aside to cool slightly.

In the small bowl of an electric mixer cream the butter. Add sugar and beat at moderately high speed for 2 to 3 minutes. Add yolks one at a time, beating until each addition is thoroughly incorporated.

Beat in chocolate and then, on lowest speed, gradually beat in the almonds, scraping the bowl with a rubber spatula as necessary to keep mixture smooth. Transfer to a large mixing bowl.

In the large bowl of an electric mixer beat the salt with the whites until they hold a definite shape, or are stiff but not dry. Stir a large spoonful of the whites into the chocolate and then, in three additions, fold in the balance. Turn into pan. If necessary, level by rotating pan brisking from side to side.

Bake for 20 minutes at 375 degrees. Reduce oven temperature to 350 degrees and bake for an additional 50 minutes. Do not overbake. Cake should remain soft and moist in the center.

Wet and slightly wiring out a folded towel and place it on a smooth surface. Remove spring form from oven and place it directly on the wet towel. Let stand 20 minutes. Remove sides of spring form Place a rack over cake and carefully invert. Remove bottom of form and paper lining. Cover with another rack and invert again to cool right side up. The cake will be about 1 3/4-inches high.

When the cake is completely cool, placed four strips of wax paper around the edges of a cake plate. Gently transfer cake to the plate, bottom up.

Prepare the icing: Scald cream in a medium-size heavy saucepan over moderate heat until it begins to form small bubbles around the edge or a skin on top. Still over heat, add instant coffee and stir briskly with a small wire whisk until dissolved. Add chocolate. After 1 minute remove from heat and stir with wire whisk until chocolate is melted and mixture is smooth. Transfer to a small bowl or place the bottom of the saucepan in cold water to stop the cooking.

Let mixture stand at room temperture for 15 minutes or more, stirring occasionally until it reaches room temperature. Stir (do not beat) and pour all over the top of the cake. Use a long narrow metal spatula to smooth the top, letting a bit of the icing run down the sides. Use a metal spatula to smooth the sides. After about 5 minutes remove the wax paper strips.