Heat olive oil in a large sautepan over medium-high heat. Add the chicken and cook until no longer pink, about 5 minutes. Remove chicken from pan and set aside. Add half-and-half and salt and pepper to taste, and stir to blend. Bring to a boil. Reduce heat and simmer until mixture is reduced a bit, about 10 minutes. (Mustard added later will quickly thicken it.) Transfer warm pasta to a warmed serving bowl. Whisk mustard into cream mixture. Return chicken to sauce, reduce heat to low and cook until heated through. Do not boil. Spoon chicken mixture over pasta and toss thoroughly. If desired, garnish with chopped parsley. Serve immediately.