SMOOTH AND creamy, almost verging on sweet -- that's how a good ricotta cheese should taste.

Ricotta is not just high-priced cottage cheese packed in fancy plastic containers. In fact, it almost makes me shudder when people say, "If you put cottage cheese in the blender it's all the same."

Not true. Ricotta is a unique cheese that stands alone. Those same people who use substitutes also often wonder why their results are disappointing.

Although ricotta does have some characteristics in common with cottage cheese, it is not much more like it than, say, cream cheese.

Ricotta originally developed as a by-product made from the whey left after the curds of the milk had been used for other cheeses. Therefore, it has always been popular in the poorer areas of the world.

Of course, in the affluent United States it has not been necessary to use leftover whey exclusively. Our domestic ricotta is made from either whey plus whole milk, skim milk plus whole milk, or just whole milk -- the last especially being the case on the East Coast. Unfortunately, this makes it higher in calories and fat than its European couterparts, but it also makes it richer and denser.

Ricotta cheese is usually available at the supermarket in 15-ounce (about 2 cups) and 2-pound (about 4 cups) cartons. Be sure to check the "pull date," as old ricotta can become terribly sour.

It can also be purchased loose in bulk amounts at Italian (and sometimes Greek) specialty stores.

As with any other cheese, each version tastes slightly different and has a texture varying from the others. Some ricottas are creamier, others are curdier. Some are naturally sweeter, others are blander, and so forth. I suggest trying a variety and choosing the one you prefer.

Dessert could hardly be easier than a small dish of ricotta mixed with a dash each of honey and vanilla extract, and sprinkled with chopped nuts or wheat germ. But ricotta can also warrant more elaborate treatment. RICOTTA SNACKS

These take only a few minutes to make -- the perfect treat for last-minute company. SWEET VERSION (Makes about 20) Raisin or whole wheat bread 1 cup ricotta cheese 1 large egg 1/2 teaspoon grated orange peel, orange part only 1/4 teaspoon cinnamon 1 teaspoon honey Walnut or pecan pieces SAVORY VERSION (Makes about 20) Whole wheat bread, rye bread or crackers 1 cup ricotta cheese 1 large egg 1/2 teaspoon grated onion (or 1/8 teaspoon onion powder) Pinch salt 1/4 teaspoon paprika 1 tablespoon grated parmesan cheese

For either version, cut bread into small squares or rounds, about 1 1/2 to 2 inches in diameter, and toast. (Not necessary with crackers.)

Mix ricotta, egg and remaining ingredients except nuts for sweet version and parmesan cheese for savory one. Place a tablespoon of ricotta mixture on each piece of toast or cracker.

Top sweet snacks with a light sprinkle of nuts, savory ones with parmesan. Place snacks under broiler for 1 to 2 minutes, or until golden brown and puffy. Serve immediately. FETTUCINE WITH RICOTTA SAUCE (4 side-dish servings, 2 main-dish servings)

a new version of that famed pasta dish originated by Alfredo -- this one is nourishing enough to be a main course. 8 ounces whole wheat, spinach or enriched fettucine* 1 1/2 cups ricotta cheese 1/2 cup plain yogurt 1 large egg 1/4 cup freshly grated parmesan cheese Salt and freshly ground pepper to taste 1/2 teaspoon basil (optional) 2 tablespoons finely chopped parsley

Start the fettucine cooking, following the directions on the package.

Put the ricotta, yogurt, egg and parmesan in a blender or food processor and process until smooth.Pour mixture into the top of a double boiler and slowly heat over simmering water, stirring constantly, until sauce is warmed through. (Do not overheat, or it may develop an unpleasant texture.)

Season sauce with salt and pepper and basil, if desired. Pour sauce over cooked and well-drained pasta, and toss gently. Garnish with parsley. Serve immediately.

*(This is especially good with homemade fettucine.) RICOTTA-APPLE SALAD WITH AVOCADO DRESSING (4 servings) 1 1/2 cups ricotta cheese 1/2 cup chopped walnuts, toasted if desired Lettuce or spinach greens 1 large red apple, cored and thinly sliced (but not peeled) Avocado Dressing: 1/2 soft, ripe medium avocado, peeled and cubed 1 tablespoon light or heavy cream 3 tablespoons vegetable oil 1 tablespoon lemon jucie Salt and pepper, to taste

Form the cheese into 1-inch diameter balls; then roll in the walnuts. Refrigerate while preparing the rest of the salad.

Place greens in the bottom of individual salad bowls; then neatly arrange the apple slices and cheese balls on top. Pour a little avocado dressing over each serving.

To make dressing, place all ingredients in a blender or food processor, and process until smooth. Or, mash the avocado with the cream, by hand; then add the oil and lemon juice and mix well. Adjust the seasonings to taste.

Note: This salad can be turned into a main dish by the addition of some chilled, cooked shrimp. RICOTTA PANCAKES (Makes about 16 3-inch pancakes)

Perfect for a special breakfast, or even dessert. 1 cup ricotta cheese 3 large eggs 2 tablespoons melted butter or oil 1/4 cup flour 1 tablespoon honey or sugar Pinch salt

Put all ingredients in a blender or food processor, and process until smooth and creamy. Heat a lightly greased griddle or skillet over medium heat. Use a spoon to pour 2-tablesppon measures of batter into small circles on the pan.

When bubbles form over the surface, turn and cook pancakes until lightly browned on the bottom. Serve immediately with fresh fruit or jam.

Note: To reheat cooled pancakes or those made in advance, place in a single layer on a baking sheet. Cover with foil, and heat in a 375-degree oven for 5 minutes. LEMONY-LIGHT RICOTTA CHEESECAKE Crust: 1 1/2 cups flour 2 tablepoons sugar 1 teaspoon grated lemon peel, yellow part only 1/2 cup butter, softened 1 large egg, plus one yolk 4 teaspoons marsala wine, sherry, brandy or water Filling: 3 cups ricotta cheese 1/3 cup, plus 2 tablespoons sugar 4 large eggs, separated 1/4 cup flour 3 tablespoons lemon juice 1 tablespoon grated lemon peel, yellow part only 1/8 teaspoon cream of tartar 2 or 3 tablespoons pine nuts (pignoli) or slivered almonds

To prepare crust, mix flour, sugar and lemon peel together in a bowl. Cut in butter until mixture resembles cornmeal. Add whole egg, yolk and wine or other liquid, and mix with a fork to form a smooth dough.

With floured fingertips, press dough into bottom and 2 inches up sides of a 9-inch springform pan. (Dough will be about 1/8-inch thick. Make sure it is not too thick where sides meet bottom of pan.) Place dough-lined pan in refrigerator while preparing filling.

Place ricotta in a mixing bowl, and beat until smooth, about 2 or 3 minutes, while gradually adding 1/3 cup sugar. Add egg yolks, flour, lemon juice and lemon peel, and beat until creamy and well-mixed. (You can use a food processor for this step, if desired.)

In separate clean bowl, beat egg whites with cream of tartar until frothy. Gradually add remaining 2 tablespoons sugar and continue beating until stiff peaks form. Fold egg whites completely into ricotta mixture. Pour into prepared shell. (Do not worry if center of mixture is slightly higher than edge of dough.) Sprinkle top with pine nuts or almonds.

Bake in a preheated 400-degree oven for 10 minutes, then reduce heat to 350 degrees and bake an additional 35 to 40 minutes, or until top is golden brown and cake has set. Cool, then refrigerate at least 4 hours or overnight.

Note: Top of cheescake may rise and crack as cake bakes. It should sink back perfectly in place as cake cools.