For the pasta:

1. Boil the pasta in salted water until al dente. The water should be as salty as sea water. I use about 2 tablespoons.
2. Drain pasta, reserving some of the cooking liquid to thin the Ricotta Pesto as needed.
3. Toss drained pasta with 1 tablespoon butter.

To make in the food processor:

1. In the bowl of a food processor, combine basil, olive oil, pine nuts, minced garlic, optional lemon juice, and salt to taste. Process until creamy.
2. Transfer to a bowl and mix in the two cheeses, butter, and ricotta.

To make with mortar and pestle:

1. Combine basil, pine nuts, minced garlic, and salt to taste (coarse is better in the mortar). Using the pestle with a rotary, grinding motion, grind the ingredients into a paste against the sides of the mortar.
2. Add both cheeses and the optional lemon and using the pestle grind into the paste.
3. Pour in olive oil in a thin stream and beat until incorporated with a wooden spoon.
4. Stir in butter and ricotta.

Combine pasta and sauce:

1. Toss the Ricotta Pesto with the hot, buttered pasta, adding reserved pasta water as necessary to make a sauce that clings to the pasta. I stir about ½ cup of the reserved water into the pesto before adding to the pasta. Salt as needed to taste.