Cook pasta in a large pot according to package directions. Add asparagus to the pot during the final 2 minutes of cooking time. Drain, reserving ½ cup cooking water.
Return the pasta mixture to the pot; stir in chicken, pesto, salt and pepper. Stir in the reserved cooking water, 1 tablespoon at a time, to reach desired consistency. Transfer the mixture to a serving dish; sprinkle with Parmesan and garnish with basil, if desired. Serve immediately.
