Cook Pasta according to package directions, adding broccoli during last 2 minutes of cooking time; drain
Melt butter in a dutch oven or deep skillet over medium heat; whisk in flour, and cook 1 minute. Gradually whisk in milk; cook, stirring constantly , 3 to 5 minutes or until thickened.
Add 2 cups cheese, mustard, salt and pepper, stirring until cheese melts. Stir in chicken and Broccoli. Serve immediately.
Recipe prepared by registered dietitians from St Vincent's Health System