In a mixing bowl, combine ground beef, breadcrumbs, beaten egg, salt, and black pepper. Mix well.
Form the mixture into small meatballs.
In a skillet over medium heat, cook the meatballs until browned on all sides. Remove from heat.
In a baking dish, spread a layer of cooked pasta, followed by a layer of marinara sauce, meatballs, and shredded mozzarella cheese. Repeat the layers until all ingredients are used.
Bake in the preheated oven for 30-40 minutes, or until the cheese is melted and bubbly.
Let the casserole cool for a few minutes before serving.
Notes:
Feel free to add your favorite herbs and spices to the meatball mixture for extra flavor.