Chicken Cheese Ziti

1 lb penne pasta
2 large chicken breasts
2 T butter
4 T Flour
1 t salt
2 1/2 c milk
2 c cheese
4 T Parmesan cheese
4 T dry Italian bread crumbs

Cook pasta and set aside.  Cook chicken and shred.  In a skillet, melt butter and stir in flour and salt.  Add milk slowly stirring until smooth.  Bring to a boil, cook and stir for 2 more minutes or until thickened.  Remove from the heat and stir in 1 1/2 cups of cheese.  Keep stirring until melted and smooth.  Combine sauce, pasta, and chicken.  Transfer to a baking dish coated with nonstick cooking spray.  Sprinkle with Italian bread crumbs, parmesan cheese, and last 1/2 c of cheese.  Bake covered at 350 degrees for 20 minutes.  Uncover and continue baking for another 15 minutes or until cheese is melted and slightly browned.