Pesto is one of a handful of sauces that have survived since the Middle Ages, when nuts were a common thickener. It combines pine nuts, garlic, olive oil and good Parmesan cheese with large quantities of fresh basil, making a richly aromatic paste. The sauce freezes well, so it provides an opportunity to preserve the summer-fresh flavor of basil into the cold months. Pesto requires no further preparation once it is made or thawed, so pasta with pesto sauce is a quick and convenient meal for any time.
Bring 5 qts. of salted water to a full rolling boil in a 6-quart pot or saucepan. Add the pound of spaghetti, stirring immediately with a wooden spoon to prevent the strands from clumping together.
Cook the spaghetti at a full boil for eight to 10 minutes, as directed on the packaging, or until it is "al dente" when tasted. This means that the noodles are tender to the tooth, and have a pleasantly firm texture when chewed.
Drain the pasta in a colander, reserving about 3/4 cup of the cooking water in a small bowl. Return the pasta to the pot, and toss with 3 to 4 oz.. of pesto sauce, until it is well coated. Slowly add the cooking water in small amounts, continuing to toss the pasta, until the pesto is smooth and has reached the consistency of heavy cream.
Mound the spaghetti into a large preheated serving dish, or individual pasta plates. Garnish with a sprinkling of shredded Parmesan cheese, and a fresh basil leaf or two if they are available. Serve with additional Parmesan cheese on the side, for diners to add as they wish.
Traditional pesto is made with fresh basil, but many recipes are now available for variations on the theme. Feel free to experiment with whatever ingredients are fresh and seasonal in your location.