Cut the chicken into cubes. Spray a crockpot with cooking spray. Add chicken, Ranch seasoning, chicken broth, minced garlic, and broccoli to a slow cooker.
Cook on low for about 3-4 hours or until chicken reaches 165 degrees.
Boil pasta for 3 minutes and drain. This will only parboil the pasta which is important, so that the pasta doesn't overcook in the crockpot.
In the crock pot combine pasta, milk, cheddar cheese, dry mustard seasoning, and cream cheese.
Stir everything together and cook on low for about an hour. Stir at least a few times during this hour.