Cooking time: 3 to 4 hours.
8 cups of cooked elbow macaroni ( do not rinse )
2 T oil
1~13 oz. can  evaporated milk
2 cups milk
3 cups of mild shredded cheddar cheese
3 cups of medium sharp shredded cheddar cheese
1 cup of cubed processed cheese
2 beaten egg's
1/4 cup melted butter
1 T minced onion ( or 1 tsp. grated onion )
salt and pepper to taste
Toss the cooked macaroni with the oil and melted butter. Add the remaining ingredients. Pour into a lightly greased Crock Pot ( or use any cooking spray ). Stir well and cover and cook on high for 1 hour. Then turn on low for 3~ 1/2 more hours. Stir occasionally. If it's to thick, thin with a little milk.

The Lighter Side; 
Substitute; 
Olive oil
cooking spray
No fat evaporated milk
Egg substitutes
Low fat cheese
Diet margarine