Winter soups are a luxury for the home cook: the effect of these nearly complete meals-in-a-bowl is far greater than the effort. They are not only easy to make, even if some require a day of unattended simmering. They are also inexpensive, often relying on beans, cheap cuts of meat or bones for their flavor. And best of all, they improve when made ahead and refrigerated or frozen until needed.

The first is the traditional Scottish solution to the problem of what to do with the old barnyard cock who has outserved his usefulness. The chicken is placed in a pot with a chunk of stewing beef and is covered with leeks and water and simmered until everything is tender. Toward the end of the cooking, some pitted prunes are added to sweeten the soup slightly and to balance the flavors. The soup is big and hearty in flavor and strength and the prunes make an unusual but welcome addition.

Second is a classic, a black-bean soup flavored with madeira toward the end of the cooking. Here a stock is made before the beans are added, then the soup is cooked and pure'ed in a food processor. Thick and delicious, this robust soup needs nothing other than some crusty bread to make a quick winter meal.

And finally, a fish soup much like the soups made in the south of France. The herbs and vegetables give a hint of Provence, and although there are three steps (first making a stock, then making the soup and then pure'eing it), the process is quite simple.

The soup is filling, yes, but it also retains a lightness about itself, so that guests won't feel overwhelmed by it.

The rouille, the final garnish added to the soup by each guest just before taking his first sip, isn't quite as hot as some rouilles in the south of France would be, but warn your guests to be careful anyway. BLACK BEAN SOUP (12 servings) 1/3 cup oil 2 large onions, chopped 4 garlic cloves, chopped 2 shallots, chopped 2 medium carrots, peeled and chopped 4 medium leeks, white parts only, cleaned and chopped 1 celery rib, chopped 2 bay leaves, crumbled 1 smoked ham hock, split in half 2 pounds beef bones, cracked 1 pound veal knuckes, cracked 1 tablespoon freshly ground black pepper 4 to 5 quarts cold water 2 cups black beans, soaked overnight in cold water to cover 3/4 cup madeira Salt Freshly ground black pepper Chopped parsley Paper thin lemon slices 2 hard-cooked eggs, finely chopped

Pour the oil into a large stockpot and set over medium high heat. Add the onions, garlic, shallots, carrots, leeks, celery and bay leaves and saute' until vegetables are tender, about 6 to 8 minutes. Add the ham hock, beef and veal bones and the pepper and cook for 8 to 10 minutes, stirring occasionally. Add the water and bring to a boil. Reduce the heat and simmer, partially covered so very little of the liquid escapes, for 8 hours.

Add the beans to the soup and simmer for another 2 1/2 to 3 hours, stirring occasionally. Add more water if the soup becomes very thick or if there isn't enough water to cover the beans. When finished cooking, remove from the heat and discard the bones. In batches, pure'e the soup in a food processor or blender until very smooth. Taste and adjust seasonings. Add the madeira, bring back to a boil then reduce the heat and simmer for 15 minutes. Serve hot garnished with parsley, lemon slices and chopped hard-cooked eggs. COCK-A-LEEKIE (16 generous servings) 1 fowl, about 5 pounds, cut into serving pieces, excess fat removed (substitute roasting chicken) 2 pounds beef shin, cut into 4 or 5 pieces 18 to 20 medium size leeks, dark green tops removed, cleaned and thinly sliced Salt Freshly ground black pepper 1/2 pound pitted prunes

Combine the fowl, beef chunks and leeks with a little salt and pepper in a large pot, about 12 quarts. Fill with cold water.

Bring to a boil over medium heat, then reduce flame and simmer, partially covered, for 4 to 4 1/2 hours.

Using a slotted spoon or tongs, carefully remove the chicken and beef. Skin as much fat as possible from the surface, then add the prunes and simmer for 40 minutes. While prunes are cooking, spread the chicken and beef on a large platter and cool in the refrigerator. When cool enough to handle, in about 25 to 30 minutes, pick over the chicken and beef. Remove the bones, skin and any gristle in the beef and shred or dice the meats.

Combine the diced meats with the skimmed broth and taste. Add salt and pepper as needed and simmer for 10 to 15 minutes longer. MARSEILLES-STYLE FISH SOUP WITH ROUILLE (8 servings) 1/4 cup olive oil 1 large onion, finely chopped 2 leeks, white part only, cleaned and finely chopped 2 cups canned, peeled Italian plum tomatoes, seeded 4 garlic cloves, finely chopped 1 bay leaf, crumbled 1 teaspoon oregano 1/2 teaspoon thyme 1/4 teaspoon crushed fennel seeds About 2 1/2 pounds fish heads, bones and scraps (thoroughly rinsed under running cold water) 2 pounds white fish fillets, such as sole or striped bass 1/2 pound orzo (substitute or small-sized pasta) 1/2 teaspoon saffron (optional) Salt Freshly ground black pepper For garnish: garlic croutons, grated parmesan cheese, rouille (recipe follows)

Pour the oil into a large soup pot and place over medium heat. Add the onion, leeks, tomatoes, garlic, bay leaf, oregano, thyme and fennel seeds. Saute', stirring occasionally over low heat until vegetables are tender, about 6 minutes.

Add 2 1/2 to 3 quarts of cold water to the pot along with the fish heads, bones and scraps and bring slowly to a boil. When the water reaches a full boil, reduce the heat and simmer for 40 to 45 minutes. Strain the soup, discarding the solids.

Add the filleted fish to the soup and cook for 15 minutes, or until fish is very tender and flaky. In small batches, pure'e the soup in a food processor or blender. Pure'e some of the soup very finely, and some of it a little less well pure'ed to add some texture to the soup. Return the pure'ed soup to the pot and add the orzo. Stir in the saffron, if using, and season with salt and pepper to taste.

Bring back to a boil over medium high heat and cook until pasta is tender, about 15 minutes.

Serve garnished with garlic croutons, grated parmesan and rouille. ROUILLE 6 garlic cloves 2 small dried red peppers 2 tablespoons soft white bread crumbs 1/4 cup olive oil 1 tablespoon tomato paste 1/2 teaspoon paprika 1/2 teaspoon hot pepper sauce

Combine all the ingredients in a food processor and process until smooth. If very thick, thin to the consistency of a loose mayonnaise with a little of the soup or more oil.