First Cook the pasta according to package (Al dente) then drain. While pasta is cooking, prepare the chicken. Using a 12-inch skillet or stove top grill heat 1 tablespoon olive oil. Split the chicken breasts, so they’re not so thick. This will help them cook more evenly.

Add the chicken breasts and sprinkle with salt and pepper. Cook and brown on both sides until chicken is cooked, browned and the juices run clear (about 10 minutes). Remove chicken to a plate, set aside and cool. Preheat oven to 350 degrees. While chicken is cooling start on the sauce. 
 
In a separate large skillet melt the butter; add the onion and garlic and cook for 1 – 2 minutes. Add the flour and mix using a wire whisk. Mix until bubbly and it starts to take on a bit of color. 

Add the heavy cream and milk; mix to combine. Bring mixture to a boil and then reduce hit to medium and simmer for about 5 minutes. Add 2/3 cup of cheese and blend using a wire whisk. Cook mixture an additional 5 minutes until the sauce starts to thicken up. 
 
The sauce will be thick enough when it coats the back of a spoon. Remove sauce from heat. Cut the chicken into bite size pieces and add to a large bowl. Add the cooked and drained pasta and the sauce last. Mix everything to combine. 

Spray a 8 x 8 inch square baking pan with non stick spray. Add the pasta mixture to the pan and sprinkle with an additional 1 cup of cheese. Sprinkle with pepper and bake for 30  minutes or until bubbly and golden brown.  Garnish with a sprinkle of Italian seasoning.