Cook the pasta according to the package directions. Drain and return it to the pot.
Add the artichoke hearts, spinach, Parmesan, 1 cup of the mozzarella, and ¼ teaspoon pepper to the pasta and toss to combine.
Heat broiler. Transfer the pasta mixture to a shallow 2-quart (or 8-inch square) broilerproof baking dish. Sprinkle with the remaining cup of mozzarella.
Broil until the cheese is browned in spots, 2 to 3 minutes.