Set your slow cooker on the low setting, and spray the inside with cooking spray.
Parboil the macaroni in salted water for 6 minutes.
While the macaroni is cooking, in a small mixing bowl, whisk together, the melted butter, evaporated milk, cheddar cheese soup, sour cream, eggs, and seasonings. Whisk until fully combined.
After cooking the macaroni for 6 minutes, drain well. Add to the slow cooker
Pour the cheese sauce over the macaroni along with 3 cups of shredded triple cheddar cheese.
Stir all of the ingredients together until the macaroni is coated and the sauce is evenly distributed.
Cover and cook on low for 2 hours. After 2 hours, remove the lid and check the middle for doneness. If needed, add additional cooking time in 20-30 minute increments or until the macaroni is tender. (Time may vary slightly depending on how your slow cooker cooks)
Sprinkle the remaining cheese on top. Replace the lid and continue to cook for an additional 15 minutes to allow the cheese to melt.
Keep warm until serving.