Start by spraying the inside of your crockpot with cooking spray. Place the cubed chicken, broccoli florets, Ranch seasoning, chicken broth, and minced garlic into the crockpot. Cover and cook on the low setting for 3 to 4 hours, or until the chicken is cooked through and the broccoli is tender.

While the chicken and broccoli cook, bring a pot of water to a boil. Add the pasta and cook for only 3 minutes, then drain well. This short boil prevents the noodles from becoming too soft later.

Once the chicken and broccoli are done, add the parboiled pasta, shredded cheddar cheese, cream cheese, whole milk, and dry mustard powder to the crockpot. Stir everything together until well combined. Cover and cook on low for another hour, stirring occasionally, until the cheese is fully melted and the pasta is tender.

Serve the mac and cheese in bowls.