Bring a large pot of salted water to a boil. Add 3 cups of dry elbow macaroni and cook until al dente, about 7-8 minutes. Drain and return to the pot. Stir in 4 tablespoons of salted butter until melted and set aside.

In a large mixing bowl, whisk together 2 cans of evaporated milk, 1/3 cup of milk, 2 large eggs, and 1/4 teaspoon of garlic salt until smooth.

In a separate bowl, combine 4 cups of shredded cheddar cheese and 2 cups of shredded mozzarella cheese.

Preheat the oven to 375°F (190°C). Lightly spray a 9×13 inch baking dish with non-stick cooking spray. Layer 1/3 of the buttered macaroni in the dish and sprinkle with 1/3 of the cheese mixture. Repeat the layering process two more times, ending with cheese on top.

Evenly pour the milk and egg mixture over the layered macaroni and cheese. Sprinkle 1 teaspoon of paprika over the top.

Place the dish in the oven and bake for 25-30 minutes, until the top is golden and bubbly and the center reaches 165°F on a food thermometer.

Remove from the oven and let cool for a few minutes before serving.