Preheat the oven to 350 degrees F (175 degrees C). Lightly grease a 2-quart baking dish.
Boil macaroni in a large pot of salted water until barely done, about 5 minutes. Drain and set aside to cool slightly.
Whisk milk and egg together in a large bowl; stir in cheese and butter.
Place par-boiled macaroni in the prepared baking dish. Pour milk mixture over macaroni, season with salt and pepper, and stir until combined. Press mixture evenly into the baking dish.
Bake, uncovered, in the preheated oven until top is golden brown, 30 to 40 minutes.
Serve hot and enjoy!
