Bring 2 quarts water to a boil in a large pot for the macaroni. Stir in 1 1/2 teaspoons salt and the macaroni and cook until almost tender but still a little firm to the bite.
Meanwhile, mix together the eggs, half of the evaporated milk, mustard, 1/2 tsp salt, and 1/4 tsp pepper
Drain the pasta and return it to the pot. Set the pot over low heat and stir in the butter until melted.
Stir in the egg mixture and half of the cheddar. Continue to cook over low heat, gradually stirring in the remaining milk and cheddar, until the mixture is hot and creamy, about 5 minutes. Season with salt and pepper to taste.