Step 1

In a large pot, bring 4 quarts water to boil. Stir in the pasta and 1 tablespoon salt, then cook, stirring occasionally, until al dente. Reserve 1½ cups of the cooking water, then drain the pasta and return it to the pot.

Step 2

In a blender, combine the ricotta, the whole pistachios, oil, Parmesan, basil, chives, ½ teaspoon salt and ¼ teaspoon pepper. Add 1 cup of the reserved pasta water and blend until creamy, about 1 minute; the pesto should have a consistency similar to yogurt.

Step 3

Pour the pesto over the pasta and stir, adding more reserved pasta water as needed so the sauce coats the noodles. Taste and season with salt and pepper. Serve drizzled with additional oil and sprinkled with the chopped pistachios.