Whisk the evaporated milk, whole milk, eggs, salt, pepper and paprika together in a bowl.
Combine the cooked macaroni, 2 1/2 cups of the combined cheese and the butter cubes in a greased 6-quart crockpot.
Pour the milk mixture over and stir until every piece of pasta is coated.
Cover and cook on low for 2 to 2 1/2 hours, stirring every 30 minutes, until the sauce is thick and the edges are set while the center still wobbles gently.
Top with the remaining cheese, cover, and cook 10 more minutes until melted.
Serve warm directly from the crockpot.
Good to Know
Undercook the pasta by a full minute or two before it goes in; it keeps absorbing liquid in the crockpot and overcooks fast otherwise.