Good ingredients essential for Northern Italian cooking

''In Italy there was always an extra aunt or someone. I didn't have to worry about making food ahead of time. Here you have to organize in a different way.''

Anna Nathanson was stirring chicken livers as she stood at the stove in a large, airy kitchen in Newton, Mass. The livers were for crostini, a spread of livers and prosciutto cooked together and served on toast as an antipasto.

It was to be the first course of the elegant Italian meal that Mrs. Nathanson agreed to prepare, and which she might have served to guests in her native city of Florence.

The dishes she chose are emblematic of northern Italian cuisine, simple and direct, with no complicated sauces or strong spices to mask the flavors of the ingredients.

The roasted squabs, for example, are gently seasoned with sage, juniper berries, and lemon; and a molded artichoke pudding tastes faintly of Parmesan and nutmeg. The dessert, most complex in taste and preparation, is a spectacular meringue and chestnut torte that Mrs. Nathanson created.

Mrs. Nathanson pointed out that meringue has been around for a long time. Italians have been baking it since the 15th century, when it was eaten with honey and nuts and candied fruit.

A handsome woman with high cheekbones and very blue eyes, Mrs. Nathanson has a good-humored down-to-earthness that seems to go along with an education in some of life's basics, especially food.

Mrs. Nathanson puts a great deal of emphasis on tasting. A dish must first of all please the palate of the cook, which is why, she explains, when her students use her recipes, the food always varies in taste, no matter what their culinary talents.

But she is most emphatic about choosing ingredients carefully. ''The important thing is the quality of what you're using.''

The basic ingredients for Northern Italian cooking are readily available, although it takes some searching to find the best. The finest Parmesan cheese, for example, is Parmigiano Reggiano, which is from the most fertile valley in Italy, where the cows' milk picks up a distinct flavor from the region's grasses. The cheese ages for two years, quite a bit longer than Grana, a more moist and mild Parmesan made for eating.

Visting relatives from Italy keep Mrs. Nathanson supplied with a strongly flavored olive oil that is made from the second squeeze, just as grade-B maple syrup is made from the second run of sap. If you don't happen to receive visitors from Florence, she recommends a brand called Bue. Here are some of her recipes. Crostini 1/4 cup finely minced onions 1/4 cup butter Squab livers of 1/2 pound chicken livers, chopped 2 slices prosciutto 1/2 bay leaf 3 crushed juniper berries Juices from the cooked squab or 1/3 cup beef broth Buttered and toasted triangles of bread

Heat butter and add onions, cooking until transparent. Add chopped livers, bay leaf, juniper berries, prosciutto, and pan juices and cook slowly until the liver is done.

Put everything in the blender and blend on low speed. Top each triangle of bread with the liver pate. Roast Squab 6 squabs 12 fresh sage leaves 6 prosciutto slices or pancetta Juniper berries Salt and pepper 6 tablespoons butter Olive oil 1 cup broth Juice of 1/2 lemon

Clean and dry squab. Tie sage leaves under wings and spread prosciutto slices over breast. Tie with string and tuck a couple of crushed juniper berries inside the cavity.

Rub squabs with butter.

Arrange squabs in baking pan. Pour a little olive oil over them and bake at 350 degrees F. for 1 hour and 15 minutes. If birds dry out, add some broth.

Squeeze some lemon juice over squabs about 10 minutes before removing from oven. Reduce juices in pan and pour over birds. Artichoke Pudding 4 large artichokes 1/3 cup flour plus 2 tablespoons 7 tablespoons butter 1 cup milk 3 eggs Pinch of freshly grated nutmeg 1/2 or 3/4 cup Parmesan cheese, according to taste

Boil artichokes with salt and a few drops of lemon juice. When they are tender, remove and scrape pulp from leaves with a paring knife. Place in a blender with artichoke hearts.

In pan, over low heat, melt 4 tablespoons of butter and add flour. Stir for a few minutes. Then add milk gradually until sauce comes to a boil. Add salt to taste.

In another pan, melt 3 tablespoons butter. Add artichoke pulp and cook over very low heat for 5 minutes, stirring constantly. Remove.

In a large bowl, beat eggs and add cooled white sauce, parmesan cheese, nutmeg, and pulp. Mix well.

Butter an 8-inch ring mold and dust with 2 tablespoons flour. Add artichoke batter evenly. Dot with butter, cover with foil, and place pan in a water bath.

Bring water to a boil and place in oven preheated to 375 degrees F. 1 to 1 1/ 2 hours. Test with a toothpick until the toothpick comes out dry. Remove pudding from oven and allow to stand for 5 minutes. Unmold. Chestnut and Meringue Dessert 2 10-inch layers of meringue, recipe follows 1 pint whipping cream 1/2 pint heavy cream 1/2 cup sugar 1 tablespoon orange juice 1/4 teaspoon grated orange peel 3/4 cup pureed chestnuts 3/4 teaspoon candied orange peel, finely diced (optional)

Combine heavy cream with whippng cream and beat with whisk or electric beater , gradually adding sugar.

Combine half of the whipped cream with pureed chestnuts. Add orange juice and fresh and candied orange peel.

Place 1 meringue on a serving plate and spread with the filling. Cover with second meringue. Spread remaining half of whipped cream over top and sides of dessert. Dust top with cocoa . Chestnut puree 1 pound chestnuts, peeled 3/4 cup of sugar 1/4 cup water 1 vanilla bean, split

Boil chestnuts in water to cover until very tender, approximately 1 hour. Put through a ricer. Bring sugar, water, and vanilla bean to a boil and cook, stirring constantly, until sugar dissolves. Stir in chestnuts and combine thoroughly. If fresh chestnuts are unavailable, sweetened pureed chestnuts are available in cans. Meringue layers 8 egg whites 1/2 teaspoon cream of tartar 2 cups sugar 2 grocery bags, flattened

Preheat oven to 200 degrees F. Beat egg whites with cream of tartar, using an electric mixer at low speed, for 5 minutes.

Increase to high speed and, when whites reach the soft peak stage, gradually add the 2 cups of sugar. Continue beating until the egg whites are thick and glossy.

Trace 2 10-inch circles on brown paper bags. Fill circles with equal amounts of meringue and spread evenly.Or use a pastry bag with a number 4 star tube. Fill pastry bag with meringue and pipe meringue into each of the outlined circles, beginning on the outside.

Place brown paper bags on the middle shelf of oven for 2 hours or more; the time will vary depending on the heat of the oven. Turn oven off and leave meringues to dry overnight.