BRILLANT Savarin, the Socrates of gastronomy, once wrote that a cook who creates a new dish does more for mankind than a scientist who discovers a new star. That made a lot of sense in the days before space travel and nouvelle cuisine. Lately, however, French chefs have been turning out new dishes and becoming stars at such a rate its hardly worth asking for a printed menu.

Some are as simple as they claim to be. Others are exceedingly complex, contain ingredients harder to find than a new star and are far less successful as dishes to eat than as visual works of art.

This may explain the instinctive slight shudder when Pierre Sosnitsky of Sans Souci called to say that his good friend Guy-Pierre Baumann had arrived from Paris bringing along his hit recipe for sauerkraut with poached fish. It sounds better as choucroute de poisson, but the taste of sauerkraut is strong and sharp while fish is delicate and subtle. Strange bedfellows, even on a serving platter.

Guy-Pierre Baumann, when he appeared, had nothing of the mad genius about him. Nonetheless he may be slightly mad because he and his wife, Andree, are directing not one but three restaurants in Paris: Baumann Ternes, Baltard and Napoleon are cited in the Michelin Guide (without stars but a citation in the Michelin is nothing to sneeze at).

An Alsatian by birth, choucroute was part of Baumann's diet from boyhood. He brought his provincial recipes to Paris and opened a restaurant, then another. "One day," he said, "a food critic challenged me to make a tasty, light version of choucroute. I decided to cook the sauerkraut with less grease and for less time, but kept the classic garnitures (such as smoked pork, bacon, sausages, goose meat). It was still too heavy for summer, so one warm day I made one with fish. People liked it. Now I have 12 different choucroutes on the menu at my Baumann Baltard restaurant."

One features lotte (anglefish) wrapped in bacon. Another is topped with small sausages made of fish mousse. A third uses the garnitures for couscous replacing the semolina with sauerkraut.

Among the innovations Chef Baumann introduced were: rinsing the curing juice from the sauerkraut before cooking it; keeping classic flavorings such as juniper berry, but reducing the amounts; cooking the fish with a minimum of seasoning and linking the two ingredients with a shallot-flavored cream sauce.

Baumann went into the kitchen at Sans Souci to show the chef his recipe and shared it with The Post. Tested with a few minor alterations at a dinner, it proved a great success. GUY-PIERRE BAUMANN'S CHOUCROUTE DE POISSON (8 to 10 servings) 4 pounds fresh sauerkraut 2 tablespoons butter or oil 1 cup chopped onion 2 cups dry white wine Bouquet garni of 2 cloves, 4 juniper berries, 1 small bay leaf, 1/4 teaspoon carraway seeds, 4 or 5 sprigs parsley, 5 or 6 bruised peppercorns -- all tied in cheesecloth 1/4 cup finely chopped shallots 2 cups heavy cream* Salt and white pepper to taste 1 1/2 to 2 pounds of at least 2 fin fish (choose fillets or steaks of rockfish or seabass, salmon or halibut, anglefish if available) 8 to 10 sea scallops, cut in half 16 to 20 medium shrimps 16 to 20 mussels or clams (optional) 1/2 pound smoked fish (haddock, chub, eel or salmon)

Ultra-pasturized cream from the supermarket will not obtain the viscous consistency of a sauce. Mix 1 tablespoon of cornstarch with water and stir it to the sauce shortly before serving.

Wash the sauerkraut in warm water, squeeze out the liquid and set to drain in a strainer. Prepare the bouquet garni. Heat 1 tablespoon butter or oil in a Dutch oven or other heavy casserole. Add the onions and saute until just soft. Add the sauerkraut, pour in the wine and add the bouquet garni. The liquid should not "drown" the sauerkraut, but if the level is too low, add some additional wine at this time or during cooking. Bring liquid to a boil, cover the casserole and lower the heat.

Chef Baumann cooks the sauerkraut for 10 minutes in a pressure cooker or simmers it about 1 hour atop the stove. I found the texture too crisp for my taste and cooked it an additional hour. This may be done ahead. Allow 30 minutes to rewarm the sauerkraut atop the stove or in a 350-degree oven.

At the same time, heat 1 tablespoon butter in a saucepan. Add the shallots and cook until softened. Add the cream and simmer for 10 minutes. Season to taste with salt and white pepper.

Shell the shrimps and cut the fish into serving pieces. Heat the smoked fish apart in milk. Cover the bottom of a large saute pan with half fish stock, or clam juice and half water. Bring to a boil. Add fin and shell fish and cook 3 to 5 minutes, or until fish is firm but not tough.

If using mussels or clams, wash well and steam separately until shells open. Leave in the shell.

Arrange fish atop and spoon about a third of the cream sauce over all. Pass remaining sauce in a gravy boat.