Add basil, spinach, salt and garlic to food processor with about 1 tablespoon of olive oil and pulse to combine.
Add parmesan and another tablespoon of olive oil. Puree to desired consistency, drizzle additional olive oil in as necessary. (If hot pasta water available, dribble a few teaspoons in to preserve color.)
Add additional salt to taste (some cheese is salty, but if it tastes like it's missing something, try small amounts of salt.)