Place chicken breast in a small saucepan with a lid. Cover chicken with cool water. Place saucepan on burner on low to moderate heat. Bring to a simmer; cover with lid and poach for approximately 20 minutes or until chicken is cooked. (This step can be done the night before).
Prepare the white sauce by placing the butter in a small sauce pot that has been preheated over medium heat. Once the butter foams, add flour and stir for 1 minute; try not to let the mixture turn brown. Add milk to the mixture and continue to stir until it starts to bubble. Reduce heat and simmer for 10 minutes. Add pepper, Italian seasoning and parmesan cheese to the sauce. Stir to combine.
Cook the pasta according to package directions. While pasta is cooking, preheat oven to 350° F. During the last minute of the pasta’s cooking, add the chopped broccoli to the water. Allow to simmer for one minute. Drain the pasta and broccoli. Spritz the bottom and sides of a 9 x 13 oven-proof casserole dish with cooking spray.
In a large bowl, combine the pasta broccoli with the chicken and chopped vegetables; cover with the sauce. Place in the baking dish. Sprinkle with Monterey jack cheese and cover with foil.
Bake for 20 minutes; remove foil and continue to bake until cheese is melted.
