For centuries Ligurian sailors plied the seas as part of the spice trade, bringing to Europe the exotic products of the Far East and Africa. When they returned from their long, arduous voyages, the sailors had had their fill of fish and spicy food. What they wanted instead was fare that spoke of their homeland, made from vegetables fresh from the gardens and farms that cling to the Ligurian hillsides. As a result, the dish that is now most closely identified with this region is pasta al pesto, noodles bathed in an intensely green and fragrant sauce.
Ligurians almost make a religion of their devotion to pesto sauce and its main ingredient, fresh basil. While they generally favor fresh herbs in their cooking, it is basil that inspires the most interest. There is, however, no uniformity of opinion as to the best recipe for pesto or its best uses. Every village, and for that matter probably every family, has its own recipe for pesto sauce and its favorite shape of pasta to use with the sauce. For example, the Genoese prefer a sharp, pungent pesto sauce which they serve with ravioli filled with veal and cheese. Many people opt for a mild pesto sauce, sometimes with cream or butter added. In many areas, the preferred pasta is trenette, a sort of plump local version of linguine. In still other areas, they dispense with the pasta altogether and add the pesto to their local version of minestrone or to fish soup.
Basil is quite easy to grow. Where I live in Southern California it flourishes in the yard almost year-round, but it also grows well in pots or window boxes. Your patio or balcony will take on a real Italian feel with a few pots of basil and other herbs. I frequently use some from my yard along with some from the market. My home garden lasts longer this way and I find using basil from two different places makes the pesto richer and more complex in flavor.
Traditionally, pesto sauce is made by hand with a mortar and pestle. Fortunately, we have food processors and blenders which make the job much easier. Save your energy for other things, like making fresh pasta to go with the pesto.
Pesto can be applied to just about any shape of pasta, not just ravioli or trenette, and other ingredients can be included with the pasta. I like green beans and potatoes with mine. Pesto is also excellent in many soups, from vegetable soups such as minestrone to zuppa di pesce, the Ligurian counterpart of bouillabaisse (the French even have a sauce similar to pesto, called pistou). I also add pesto to white bean soup, always just before serving.
There are lots of uses for pesto besides as a pasta sauce or as a final flavor touch for soups. It's an excellent accompaniment to any grilled or poached chicken or many types of fish. Either alone or added to mayonnaise, it can be used on sandwiches. My favorite is my "Italian ham and cheese": prosciutto, fresh mozzarella and pesto on fresh country bread. Pesto also livens up those turkey sandwiches which seem to be overrunning America, or add it to chicken salad, or use it as an hors-d'oeuvre spread or dip for fresh vegetables. The possibilities for using pesto are endless. My only problem seems to be that I never make enough.
Using Pecorino cheese and increasing the quantity of garlic will yield a more intense, sharply flavored pesto. Some people prefer to toast their pine nuts. Using walnuts yields a more woodsy flavor. The amount of olive oil can be adjusted depending on the desired final consistency (thicker or thinner).
Cook lasagna according to package directions. Rinse in cold water. Drain on towels.
Blanch zucchini in abundant salted boiling water for 6 to 8 minutes (according to size of zucchini). Rinse under cold water. Slice lengthwise in 1/4 in. strips.
Combine pesto, ricotta and yogurt and blend until smooth.
Take a 9 in. x 13 in. glass baking dish and spread a small amount of tomato sauce over the bottom. Place a layer of lasagna noodles next, then spread 1/2 pesto-ricotta mixture over the noodles. Next, make a layer of zucchini strips. Spread tomato sauce over the zucchini, then add another layer of lasagna noodles. Spread the remaining pesto-ricotta mixture over the noodles, then make another layer of zucchini strips. Spread tomato sauce over the zucchini, then add another layer of lasagna noodles. Top with tomato sauce. Sprinkle with grated cheese. Cover with aluminum foil and bake at 400 degrees for 20 minutes. Remove foil and return to oven until golden brown on top (about 5-10 minutes). Let stand 10 minutes before serving. Serve with remaining tomato sauce. Garnish with additional grated cheese and julienned basil leaves. Serves 8 to 10.