In a food processor puree the dill, parsley, oregano, lemon zest and juice, olive oil, ricotta cheese and yogurt. Transfer to a bowl and add the chives; season to taste with salt and pepper.
Drain the pasta, reserving 1/4 cup of cooking water and return it to the pot off heat. Add the herbed cheese mixture, reserved cooking water and toss. Serve immediately with slivered black olives.