Shred sharp cheddar cheese, Monterey Jack cheese, Muenster cheese, and Haravti cheese. Set aside.
Add elbow noodles, whole milk, evaporated milk, unsalted butter, seasoned salt, ground mustard, and black pepper in the insert of a 6-quart slow cooker. Stir to combine. Sprinkle the shredded cheese on top.
Cover and cook on low heat for 1 hour. After 1 hour, stir the mixture. Cover and cook for 40-50 minutes more, until the noodles are softened.
Switch the slow cooker to high heat and cook for an additional 8-10 minutes, covered, to thicken the sauce.
Serve immediately, or switch the slow cooker to warm to keep the mac and cheese warm.