Cook macaroni in boiling salted water as package directs. Drain and set aside.
In the meantime, in a saucepan over medium low heat, melt butter; add flour. Cook, stirring, until flour mixture is well blended and bubbly. Gradually stir in chicken broth and cream. Stir in cheese until melted and smooth. Add pepper, to taste, along with parsley, if using. Cook, stirring, until thickened. Add the chicken and vegetables; cook for about 1 minute longer.
Combine the sauce with cooked and drained macaroni; pour into a 2-quart casserole. Toss bread crumbs with melted butter and sprinkle over the casserole. Bake at 350° for about 25 minutes, until bubbly and browned.