Prepare pasta according to package directions; drain, reserving ¼ cup pasta water.
Place basil, oil, green onion, parsley, capers, lemon juice, mustard and garlic in food processor; pulse quickly 4-7 times until rough paste has formed. Do not over process. Add some reserved pasta water if needed to thin to desired consistency.
Season sauce with salt and pepper if desired. Toss pasta with sauce.