ADJECTIVES such as "hearty" and "robust" pale before the Tuscan soup called ribollita. Thick with vegetables and bread, and invariably topped off with a generous dousing of olive oil, the soup is (dare we say it?) just plain heavy. Fortunately, this quality is part of its appeal and, besides, it tastes wonderful. So let fragile, pallid sushi go the way of nouvelle cuisine. Ribollita is a winter soup that sticks to your ribs.

Ribollita means "reboiled" and that's what the dish is--a casual concoction of leftover soup and stale bread. Much loved by Tuscans, it is classified as cucina magra (literally, "meager cooking"), a tradition of peasant cooking that relies heavily on vegetables and carbohydrates. To say this of a dish is to pay it a back-handed compliment, for in Italy the terms cucina magra or cucina povera ("cooking of the poor") carry the connotation of good, honest food, made with natural ingredients and unsullied by fancy sauces. Filling soups such as ribollita have been eaten through the centuries not only to stretch the budget, but to satisfy the dietary restrictions of religious holidays. Some recipes call for meat, but most often it is omitted or used only sparingly to add flavor.

Many cookbooks dismiss ribollita with a line or two: For example, "Make your favorite vegetable soup and add stale bread." The average Tuscan, however, has strong views on what makes a good ribollita. Livio Cesari, a Florentine gardener whose sister provided the recipe given here, criticized my first rendition of ribollita by pointing out that I had not browned the onions adequately. Now I not only attend diligently to this detail, but believe that it is a key step in producing a flavorful base for the soup.

Some recipes specify spinach or cabbage, but many Tuscans say cavolo nero ("black cabbage") are the only kind of greens to use in ribollita. Our kale is a very close and entirely satisfactory substitute.

Another tip: The soup really does have to be reboiled. That is, leave it in the refrigerator a day or two for the flavors to blend before making the ribollita. If you don't want to wait, double the quantity of soup and eat half of it the first day topped with parmesan and accompanied by fresh bread or rolls.

Finally, take pains with the bread. Use an insipid or only partially stale bread and you'll end up with a gummy mess in your soup bowl. It seems absurd to make homemade bread only to allow it to dry out, but this is the safest route. Devised by Anita Segreti, a local teacher of Italian cooking, the recipe for Tuscan bread given here is easy to make and stands up admirably to a dunking in soup. Alternatively, experiment with any coarse, sturdy bread, preferably whole wheat. After mixing a slice with a bit of soup, try it. The bread should soften, but not disintegrate. If it does fall apart, don't persevere; just serve the soup with fresh bread on the side.

Also squarely in the cucina magra tradition are two other bread soups: acquacotta ("cooked water") and pappa al pomodoro ("tomato pap"). Unfortunately, these soups live up to their names only too well. Acquacotta is truly a modest soup, consisting of onion, garlic, parsley, red pepper, parmesan, a little bacon for seasoning, bread and, of course, plenty of water. In pappa al pomodoro--inexplicably, second in popularity only to ribollita--tomatoes are cooked with bread to a consistency so pablum-like even toddlers have been known to spurn it.

The bean and bread soup zuppa lombarda is more interesting and palatable. As Giuliano Bugialli explains in "The Fine Art of Italian Cooking," the Florentines invented this upon yielding to the Lombards after a siege in 1525. To feed the hungry invaders, thay had to make creative use of their meager food supply: beans, old bread, olive oil and broth. Zuppa lombarda is extremely simple, but for that reason it is hard to make well. One cannot sneak in canned broth or beans as in ribollita, where a multitude of other ingredients mask small imperfections. Beans, broth and bread must all be homemade. A liberal sprinkling of freshly ground pepper helps counteract the natural blandness of the soup. PANE INTEGRALE (Tuscan Whole Wheat Bread) 1 cup warm water 2 tablespoons yeast 1 tablespoon sugar 4 cups bread flour 2 cups whole-wheat flour Salt* 1 1/4 cups warm water Butter for bowl Cornmeal for cookie sheet

Pour 1 cup warm water into small bowl, sprinkle yeast and sugar on top, and allow to sit about 10 minutes. Mix with flours and salt in large bowl. Add only enough water to form a dough that cleans the bowl (the dough seems to absorb more water when made in a food processor or automatic mixer than by hand). Knead 5 minutes. Place in a buttered bowl, cover with plastic wrap and let rise until doubled in size (about 1 1/2 hours). Turn dough out on a lightly floured board. Add a little more flour and knead briefly if sticky. Let dough rest about 10 minutes, then divide into 2 portions and gently pat each into a rectangle about 10-by-6 inches. Roll each one lengthwise in jellyroll fashion and pinch edges together to make a seam, turning the ends under as you shape the loaf. Put both loaves on a cookie sheet sprinkled with cornmeal and let rise about an hour. Preheat oven to 425 degrees, drop temperature to 375 degrees as you put in the bread and cook 55 to 65 minutes.

*Authentic Tuscan bread contains only a pinch of salt, but most American palates are accustomed to about a tablespoon in this amount of bread. One teaspoon is a good compromise. FAGIOLI BOLLITI (Boiled White Beans) 1 pound dried great northern or cannellini beans Salt 1 to 2 ounces pancetta or salt pork 4 tablespoons olive oil 2 large cloves garlic, peeled 1 sprig of sage (substitute fresh or dried rosemary) Freshly ground pepper 3 to 4 peppercorns

Soak beans overnight; drain, rinse and place in large stockpot with 3 quarts cold water. Season with salt, pancetta or salt pork, olive oil, garlic, sage, pepper and peppercorns. Simmer very slowly for about 3 hours. Discard flavoring ingredients and use beans for ribollita, zuppa lombarda and other recipes. RIBOLLITA (Tuscan Bread Soup) (6 servings) 1 large onion, red or yellow 4 tablespoons olive oil 2 tablespoons tomato paste 1 small bunch kale 2 large stalks celery 3 medium carrots 1 large or 2 small zucchini

% medium potatoes Parsley Basil (optional) Salt Pepper Stock or bouillon cube mixed in water 2 cups cooked white beans (cannellini or great northern--recipe above) 6 slices stale Tuscan bread or close equivalent Garlic (optional) Extra-virgin olive oil

Chop onion and cook in oil on medium heat until golden brown (take care not to burn). Add tomato paste and about 1 cup of water. Simmer 10 to 15 minutes until dense. Add chopped kale, celery, carrots and zucchini. Chop 2 potatoes and add, putting the others in whole or halved. Season with parsley, basil, salt and pepper, and pour in enough stock or water to barely cover vegetables. When the whole potatoes are done, pure'e and return to the soup. Simmer soup 3 hours or more. During the last hour of cooking, pure'e 1 cup of the beans and add to the pot, along with the remaining whole beans. Refrigerate soup at least 1 day before serving.

If bread is not stale enough, slice and leave in 250-degree oven about 30 minutes, shaking the pan occasionally. When ready to serve, cube or break up bread, and place enough in each soup bowl to cover the bottom. (Variation: Rub cut side of peeled, halved garlic clove over each slice of bread before breaking up). Ladle soup over, then mix gently. Allow to sit several minutes until warm or tepid. Pass a cruet of extra-virgin olive oil at the table to drizzle on top of each serving. ZUPPA LOMBARDA (Bean and Bread Soup) (4 servings)

6 thick slices stale Tuscan bread 2 cups beans and 1 cup cooking liquid from fagioli bolliti 4 cups homemade beef broth Salt Freshly ground pepper Extra-virgin olive oil

Cut bread slices into thirds and place in bottom of soup tureen or divide among individual bowls. Heat beans and broth in separate saucepans. Spoon beans with their liquid over the bread, then add enough broth to cover other ingredients by 1/2 inch. Add salt as necessary and abundant black pepper. Cover tureen (or position plates over bowls) and allow to sit about 10 minutes before serving. Pass olive oil at table to sprinkle onto soup, which is served barely warm.