1. In a food processor, combine basil, walnuts Parmesan, garlic, lemon juice, salt and pepper and 3 tablespoons of water. Process until a paste forms.
2. With the motor running, add oil in a thin stream. Process until very smooth, about 1 minute
3. In 5-6 quarts of boiling water, add 1 tablespoon of salt.
4. Cook 8 ounces of spaghetti until al dente, according to package instructions.
5. Reserve 1/2 cup pasta water; drain pasta and return to pot.
6. Toss paste with Pesto, adding reserved water a little at a time to create a thin sauce that coats the spaghetti (you may not need all the water).
7. Season with salt and pepper
Serve garnished with shredded basil.