Cook the pasta according to the package directions.
Meanwhile, pulse the peas in a food processor or blender until chopped but not pureed. Add 1/2 cup of the ricotta, season with the salt and pepper, and pulse to combine.
Drain the pasta, reserving 1/3 cup of the pasta water. Return the pasta to the pot. Add the pea puree and reserved pasta water and toss. Divide the pasta among individual bowls. Top with the remaining ricotta, a sprinkle of chives, and a drizzle of oil.
Tip: Tagliatelle (pronounced tal-ya-TEL-ee) are pasta ribbons that are wider than fettuccine. Pappardelle (pa-par-DEL-lay) are even wider. Both work well with somewhat chunky sauces.