Recipes that make use of seasonal foods are a traditional way to achieve kitchen economy. This year, despite the season, rising food costs have taken many preparations put of the economy class, even if some of the ingredients are home grown.

For an illustration, let's make pesto, that superb Italian peasant concoction. Pesto alone has inspired countless cooks to begin herb gardens so they can harvest a supply of basil. But to make this pasta-topping, you need olive oil (at $1 a cup), imported Italian cheese (at $5 to $7 a pound), pine nuts (at $3.75 a half-pound), garlic and freshly ground pepper. Nonetheless, having the basil on the hand, we made a thick, pasty version with the recipe that follows. Think it with a spoonful or two of pasta cooking water. PESTO (Makes about 1 1/2 cups) 3 1/2 to 4 cups basil leaves, washed and dried 4 or 5 cloves garlic 1/2 cup pine nuts 25 grinds black pepper 1 cup (scant) freshly grated Romano cheese 3/4 cup freshly grated Parmesan cheese 3/4 cup olive oil, or olive cut with salad oil

Crush or grind garlic and pine nuts in a mortar with a pestle or in a food processor. Add pepper, then the basil leaves. When finely ground, mix in about half the cheese, then slowly add the oil. Stir in remaining cheese.

pesto may be frozen or stored in the refrigerator covered with a thin coating of oil. SPINACH AND TOMATOES (2 to 4 servings) 1 pound fresh spinach 2 tablespoons oil 2 tablespoons butter 1 clove garlic, minced 3 scallions (white and half of green portions), finely chopped 2 tablespoons chopped green pepper 1 large tomato, seeded and chopped 1/4 cup fresh basil leaves, cut in shreds Salt and freshly ground pepper to taste.

Clean spinach and parboil in salted water until just cooked. Drain, cool, squeeze out all possible liquid and chop. (This may be done ahead.)

Heat oil and butter in a skillet. Add garlic, scallions and green pepper and cook until softened. Add tomato and basil. Raise heat and cook until liquid has mostly evaporated. Add chopped spinach and stir all together. Season and allow to heat through. Serve with roast chicken or pork. PUREE OF PEAS (4 to 6 servings) 2 pounds unshelled peas 2 tablespoons butter 2 to 3 tablespoons cream Salt and pepper to taste 1/2 teaspoon sugar 1 to 2 tablespoons grated Parmesan cheese Fresh grated nutmeg to taste 1 to 2 teaspoons brandy

Shell peas and cook until tender in lightly salted and sugared water. Drain and put through the medium disk of a food mill, or puree in a food processor.

Transfer puree to a saucepan. Add butter, cream, salt, pepper and sugar. Heat through and mix well. Add cheese, nutmeg and brandy. (Exact amounts of cream, cheese, brandy, salt and pepper should be adjusted to texture and sweetness of peas and personal taste.) Thin with more cream if necessary. Serve as is with other pureed vegetables or on an artichoke bottom. VEGETABLE STEW (Makes about 1 quart) 1/2 large onion, sliced 1 large clove garlic, minced 1 large green pepper, seeded and sliced 1/4 cup olive oil 2 yellow squash, halved and sliced in 1/4-inch pieces 2 zucchini, halved and sliced in 1/4-inch pieces 1/2 tablespoon dried mixed herbs or 1 1/2 tablespoons mixed fresh herbs Salt and freshly ground pepper to taste 2 tomatoes, seeded and chopped pinch of sugar Juice of 1/2 lemon

Saute onion, garlic and pepper in oil until softened. Add squash and zucchini. Saute to coat vegetables, then add seasoning, tomatoes, sugar and lemon juice. Cover and simmer 10 to 15 minutes, or until vegetables have softened.Remove vegetables to a bowl with a slotted spoon. Turn up heat and reduce juices until thick and syrupy. Pour over vegetables, taste and adjust seasoning. Serve hot or cold, but remember to season with a strong hand if dish to be served cold.