Cook the elbow macaroni according to package directions until al dente. Drain well.

Transfer the drained pasta to a large, deep casserole dish. Add butter while pasta is hot to melt it.

Season with salt and pepper. Add 2 cups mozzarella and 3 cups cheddar (reserve 1 cup for topping).

In a separate bowl, beat the eggs until smooth, then pour over the cheesy pasta mixture. Stir until well combined.

Cover the dish tightly with foil and bake in a preheated 350°F oven for 45 minutes.

Remove foil, sprinkle the reserved 1 cup of cheddar on top, and bake uncovered for 15-30 minutes until golden and crispy.

Let rest for 5 minutes before serving.