Rigatoni with Pesto and Chickpeas

Bring a large pot of lightly salted water to a boil. Add pasta and cook as package directs. Meanwhile, process 3 ⁄4 cup chickpeas and the pesto in a food processor until smooth, scraping down sides as needed. Slowly pour 1 ⁄2 cup pasta cooking water through feed tube; process until creamy. Set a colander in kitchen sink; put the remaining chickpeas in the colander and drain the pasta. Return pasta and chickpeas to pot. Add pesto mixture and toss to mix and coat. Serve immediately, topping with tomatoes and parsley.