Place pork tenderloin, Ranch seasoning and soup into a medium sized crock pot over high heat for 4 hours or low heat for 6 hours.
Place potatoes into a large pot of cold water. Place onto stove top over high heat and bring to a boil. Once water is boiling, cook for 10-12 minutes or until potatoes are fork tender. Drain and transfer to the work bowl of a stand or electric mixer. Mix on low until potatoes are mashed then add butter, Parmesan, garlic, milk, salt and pepper. Season to taste if needed. For thinner mashed potatoes add more milk, slowly until your desired consistency.
Scoop mashed potatoes onto serving plates and top with pork chops and soup gravy from crock pot.