WHEN CLARA Maria de Amezua casually picked up a set of measuring cups and spoons during a visit to this country a few years ago, she had no idea that these simple tools would eventually inspire her to become a director of Spain's first cooking school for Americans.

But she quickly discovered that "using spoons and cups is so much more convenient than weighing ingredients as we do here in Europe," voicing this iconoclastic opinion with considerable enthusiasm between sips of cool gazpacho on a recent warm afternoon in Madrid.

"After I had tested almost my entire repertoire of Spanish regional recipes with American measurements," she added, "the most logical step was to invite Americans here to discover what Spanish cooking is really like."

An experienced hand at teaching cookery, de Amezua, along with three other women, has for four years run Alambique, a highly successful kitchen shop and cooking school located in a fashionable section of downtown Madrid. As an active member of Spain's Academy of Gastronomy, de Amezua has spent decades traveling throughout the country, collecting regional recipes virtually unknown outside of Spain and often not even known to Spaniards. She has already written one book on Spain's regional cookery and is researching Iberian recipes for another on Sephardic Jewish cuisine.

De Amezua is the first to admit that the Spanish kitchen does not rank with the French or Chinese as one of the world's greatest cuisines, but her research, she said, has proven that "the range and complexity of Spanish dishes are much greater than Americans and even the Spanish realize."

In part because of her long-abiding interest in Spanish cuisine, de Amezua will not actually do the teaching. "Once I'm in front of a group of enthusiastic cooks," she admitted with a laugh, "I can't stop talking about the foods, their histories, how they are eaten and so on." Instead, the instructor will be Basque-born Isabelle Maestre de Cardenas, who has trained at LaVarenne and the London Cordon Bleu. De Amezua will translate and answer questions in English.

The first week-long course for Americans will begin on Sept. 11 in the spacious, new kitchen facility located a few doors down from the original school and shop. Classes will be limited to 25 students. Four mornings will be taken up with the demonstration and preparation of a meal focused on one of Spain's gastronomic regions: Galicia in the north; Andalusia in the South; Castile and Estremadura in Central Spain; and Catalonia in the east. The demonstrations will include regional specialties such as Andalusian artichokes, bull's tail stew, partridge soup and loin of pork with walnut sauce.

Dishes cooked during class and additional specialties brought from home by the instructor will be served for lunch, accompanied by wines of the region, many of which are not available outside of Spain. All students will receive a notebook including the recipes and background information on Spain's regional cookery styles.

In addition, said de Amezua, organized tastings of regional cheeses and hams and a range of Spanish olives and olive oils have been arranged in conjunction with a new specialty food shop called El Gourmet de Palacio.

But de Amezua and her colleagues intend the course to go beyond familiarity with ingredients and cooking techniques. "What I hope the students will acquire," explained de Amezua, "is a feeling for our whole culture, the way of life and the character of the Spanish people. That's the only way they will really get to understand the Spanish kitchen."

To this end, the directors have scheduled afternoon trips such as to See SPAIN, H2, Col. 2 Clara de Amezua and instructor Helena Lind Learning Spanish Cooking on Location SPAIN, From H1 the Prado Museum and Royal Palace, an excursion to nearby Segovia with luncheon at a traditional country inn and a cocktail party at de Amezua's home, where typical Spanish tapas (hors d'oeuvres) will be served.

The week will close with a graduation party held at a private 17th-century manor on one of Spain's most elegant estates. "You see," explained de Amezua, "I am inviting my American students to come and share a week in Spain with me and my friends."

For a brochure outlining the course and scheduled activities, write to Marketing Ahead, 515 Madison Avenue, New York City 10022.

From de Amezua's voluminous collection of Spanish recipes, here are several regional classics. MEJILLONES RELLENOS (Stuffed mussels) (3 to 4 servings)

This Catalonian dish is well suited for a hot summer evening. It is intended to be served hot, but is also quite tasty at room temperature. 3 1/2 pounds mussels 2/3 cup Spanish olive oil 1 1/2 cups finely minced onions 1 cup finely chopped mushrooms 1/2 teaspoon minced garlic 1 tablespoon minced parsley 1 tablespoon flour 1 cup dry white wine Generous pinch of freshly ground nutmeg 1/8 teaspoon cinnamon Salt and freshly ground pepper 2/3 cup finely ground bread crumbs 1/2 pound cooked shrimp, finely chopped 1/4 cup finely minced parsley for garnish

Beard the mussels and scrub them well. Put them in a large pot with 1 1/4 cups water, cover pot and cook over high flame just until mussels open, about 6 to 8 minutes. (Do not overcook or mussels will be rubbery.) Reserve the broth. Remove the top shells of the mussels and save about half of them. Set the mussels on their half shell in 2 or 3 large, shallow baking pans. In a large skillet, heat the oil. Add the onions and cook them for 5 minutes. Then add the mushrooms, garlic, 1 tablespoon parsley and flour and cook until the mixture becomes somewhat dry. Pass the reserved mussel broth through cheesecloth to eliminate any sand and add 1 cup of this broth plus the wine to the pot. Add the nutmeg, cinnamon, salt and pepper to taste. Cook over medium heat about 15 minutes, or until mixture is slightly reduced. Stir in the bread crumbs and continue cooking an additional 7 to 10 minutes, or until the mixture resembles a thick porridge. Stir in the shrimp. Adjust seasonings. With a spoon or knife, gently pry each mussel off its bottom shell. Replace it in the shell or, in the case of large and plump mussels, snip them in half and place the second half on one of the reserved shells.

If you are planning to serve the mussels hot, set the oven to 350 degrees at this point. Then spoon enough stuffing on each shell to completely cover the mussel and fill the shell. Place in oven only until mussels are heated through and serve immediately with a garnish of minced parsley. Otherwise, allow the baked mussels to cool to room temperature and serve. PATATAS GUISADAS (Potato Stew) (4 to 6 servings)

This unusually seasoned potato stew is from La Mancha, the land of Don Quixote. It makes a good accompaniment for roast lamb or pork. 2 pounds potatoes 5 tablespoons Spanish olive oil 2 medium-sized cloves garlic, peeled 1 cup minced onions 1 large tomato, peeled, seeded and chopped 2 tablespoons finely minced parsley 1 bay leaf 1/2 teaspoon thyme 1/4 teaspoon tarragon 1 teaspoon salt Freshly ground pepper

Peel the potatoes and slice them into thin rounds. Set aside. In a large, heavy saucepan or soup pot, heat the oil and fry the garlic until golden. Remove garlic and set aside. Add the onions to the oil and saute' until they begin to turn golden. Add the tomato and cook about 5 minutes, stirring frequently. Stir in the potatoes, being sure to coat the slices with the oil. Mash the garlic and add it to the pot with the parsley, bay leaf, thyme, tarragon, salt and pepper. Stir in 2 cups of boiling water and bring to a boil. Then simmer, covered, until the potatoes are tender, about 25 minutes. Stir occasionally to prevent scorching. Before serving, adjust seasonings. If you wish to thicken the stew, remove a few potato slices, mash them, then return to pot. Discard the bay leaf and serve hot. AJA BLANCO CON UVAS (White gazpacho with grapes) (6 servings)

There are said to be more than 35 varieties of gazpacho in Andalusia, but this rich and refreshing version is likely to be the most exotic. The grapes and olive oil bring out the best in each other. 3/4 cup bread crumbs 1/3 cup milk 1 cup blanched, slivered almonds 1/2 teaspoon finely minced garlic 1/2 teaspoon salt 1 cup Spanish olive oil 3 tablespoons white wine or sherry vinegar 5 cups very cold water 1 large bunch (about 48) grapes, peeled if you wish, and seeded if necessary

In a small bowl, mash the bread crumbs in the milk. In a blender or food processor, grind the nuts. Transfer the ground nuts to a mortar and, using the pestle, mash them with the garlic and salt into a smooth paste. Press the bread crumbs in a clean cloth to squeeze out excess milk. Then, using the pestle, blend them into the almond paste. Transfer the mixture to a large bowl and, while beating continuously with an electric mixer, pour in the olive oil slowly in a very thin stream until it is well integrated. Continuing to beat, add the vinegar and then the cold water. Pass the liquid through a fine-meshed strainer. Add more vinegar or salt to taste, and chill thoroughly before serving.

To serve: If the mixture separates, stir it vigorously with a whisk. Spoon the gazpacho into individual bowls and garnish each serving with about eight grapes. (Although the grapes are traditionally peeled, you might not consider it worth the effort.)