How to Make It
Preheat the oven to 375°. Butter a shallow 2-quart gratin dish.
Stir together the mozzarella, ricotta and black pepper in a large bowl.
In a large pot of boiling well-salted water, cook the pasta until al dente. Reserve about 1 cup of the pasta cooking water, and then drain the pasta well.
Add the pasta to the cheese mixture and toss well to coat. Add about 1/2 cup of the cooking water, or as needed, to loosen the sauce. Pour the mixture into the buttered gratin dish.
In a small bowl, stir together the bread crumbs and Parmesan cheese, then sprinkle the mixture evenly over the pasta. Dot the top of the dish with the butter cubes.
Bake until the dish is hot throughout and the topping has melted, about 15 minutes. Turn on the broiler and broil the macaroni and cheese until the crumbs are golden brown, about 3 minutes. Serve immediately.