THE BEST place to start a Latin gastronomic fling is with plantains, banana look-alikes that appear in widely varying stages of ripeness.

Cooking encyclopedias give us useless information -- that plantain is an herb, that it is seasonless and, according to Andre L. Simon, it is a noxious weed that ruins a lawn. He was obviously unaware of the tropical fruit that can be eaten as a cooked vegetable.

A great story comes out of "The Food Book" by James Trager. Captain Bligh of "The Mutiny on the Bounty" fame got back to England after the mutiny and sailed off to make the same mistake again. He went back to Tahiti for the breadfruit plants, keeping his crew on short water rations, and finally got the plants to Jamaica where they grew very, very well. But in the end the natives preferred the familiar plantain and snubbed the hard-won breadfruit.

The novitiate cook might be puzzled by a mound of green plantains -- their banana look, their enormous size, their resistance to squeezing, their lack of aroma. They can be bought and eaten from very green to absolutely black. Bananas don't prepare you for such a thing.

The saavy cook with future meals in mind will lay in two or three pounds of plantains, which ripen according to some timetable of their own. But store them in a dry place with the potatoes and watch them carefully as they progress from green to a golden yellow with black spots and finally to black and slightly dessicated.

In each stage they have their own flavor -- the final black stage the sweetest and more banana-like. By then the flesh has turned soft and a light salmon color, and is usually baked in its skin and served as a vegetable with roast meats.

Prepared like potato chips, plantains have instant identification for us, a crisp bite with an elusive tropical flavor that is good served with drinks. Tostones are thick slices of plantain fried until soft, flattened, and fried again until crisp. The chips can accompany a main dish, but since they are eaten with the fingers, make it an informal Caribbean-style dinner such as chicken, black beans and rice.

In Puerto Rico, cooked and mashed plantain is used much as we use mashed potatoes, and turns up in various renditions as croquettes and fritters, and a dish lengthily called Pastelon de Platanos Maduros con Carne -- a sort of shepherd's pie.

One good cook from Jamaica found herself living in a section of the United States that was plantainless. So she picked up plantain look-alikes at the market (firm, green-tipped bananas), peeled them and tucked them in the roasting pan when she was having pork or chicken. Basted with the pan juices, they tasted almost like the real thing. PLANTAIN CHIPS 3 large or 4 medium plantains, green to medium-ripe 2 tablespoons salt 1 1/2 quarts water Fat for deep frying Salt for sprinkling

To peel plantains, make a lengthwise slash through the skin with a sharp knife and peel it away in large sections. Slice very thinly with a mandoline, food processor or a vegetable peeler and plunge into a bowl with water mixed with salt. Soak for 10 minutes, drain and dry on paper towels. Heat peanut oil or lard to 375 degrees in a saucepan or wok (which uses less fat) and add 1/3 of the plantain chips. Fry until they are a pale beige, remove with a skimmer to paper towels and salt lightly, if desired, while still hot. Repeat with the remaining plantains in two batches. TOSTONES 3 large or 4 medium plantains from green to medium-ripe 1 quart water 2 cloves garlic, peeled and crushed 2 tablespoons salt Fat for pan frying

To peel plantains, make a lengthwise slash through the skin with a sharp knife and peel it away in large sections. Slice each plantain 1-inch thick slightly on the diagonal. Plunge into the water with the garlic and salt and soak for 30 minutes. Drain and dry with paper towels.

Add enough lard or peanut oil to a large skillet to come to 1/4 inch. Heat and add as many plantain slices as will fit in the pan in a single layer. Saute' gently until soft on both sides, 5 to 8 minutes, and remove to sheets of paper toweling on a firm surface. Cover with more toweling and flatten each with the palm of your hand. Just before serving, reheat the fat and saute' the plantain again until brown and crisp in 2 or 3 batches. Drain on paper towels. PLANTAIN MEAT PIE (6 servings) For filling: 1 medium onion, finely chopped 1 large green pepper, finely chopped 1 clove garlic, minced 2 tablespoons vegetable oil 2 tomatoes, peeled, seeded, and chopped 1/2 pound lean ground beef 1/2 teaspoon wine vinegar 1/2 teaspoon oregano 1 tablespoon minced, pimiento-stuffed green olives 1 teaspoon capers 1 tablespoon seedless raisins For plantains 4 or 5 large ripe plantains (golden brown with black spots) 1 tablespoon salt 6 cups water 4 tablespoons soft butter 1/2 cup flour

First prepare the filling. Cook the onion, green pepper and garlic over moderate heat in the vegetable oil. When soft but not brown, add the tomato and cook 3 minutes. Add the meat and stir to brown, breaking up the clumps with a spoon. If the meat is very fatty, drain off some of the fat. Add vinegar, oregano, olives, capers and raisins, cover partially and cook 10 minutes over gentle heat.

In the meantime, prepare the plantains. Cut off both ends, halve crosswise without peeling, and place in a sauceplan of boiling water seasoned with the salt. Cook over a brisk flame for 25 to 30 minutes, or until soft. Drain and peel and return the plantain to the saucepan. Add flour and butter and mash to a paste.

Grease a 9-inch pie pan and spread half the mashed plantain over the bottom and up the sides. Spread the meat filling over the plantain and spoon the remaining plantain evenly over the top, spreading it evenly with the back of a spoon. Bake at 350 degrees for 30 minutes. PIONONOS (Makes 12) 3 large ripe plantains (golden brown with black spots) Lard or peanut oil for pan frying 2 large eggs 1 tablespoon flour 1 tablespoon water 1/4 teaspoon salt 3/4 cup shredded cheddar cheese

To peel plantains, make a slash lengthwise through the skin and remove the meat in large pieces. Cut each plantain lengthwise into 4 slices with a long, sharp knife. Heat 1/4 inch fat in a large frying pan and brown the plantain slices quickly on both sides and drain on paper towels. When just cool enough to handle, roll each slice around your finger, keeping one end as closed as possible -- forming into a cone, and secure with a toothpick. Beat eggs, add flour, water and salt and beat again. Stuff the cones firmly with the shredded cheese and dip in the batter. Fry in hot fat in the skillet, starting with the stuffing side down. When golden brown, remove the paper toweling, remove the toothpicks and serve immediately.