Directions:

1. Preheat and Grease: Preheat the oven to 425 degrees F (220 degrees C). Grease a 9×13-inch baking dish with cooking spray.
2. Boil Spaghetti: Bring a large pot of lightly salted water to a boil. Cook spaghetti until tender yet firm (al dente), about 8 to 10 minutes. Drain and rinse with cold water.
3. Prepare Spaghetti Mixture: In a large bowl, mix 1/2 cup mozzarella, milk, beaten egg, salt, and garlic salt. Add the drained spaghetti and mix until well combined. Spread the mixture into the prepared baking dish.
4. Bake Initial Layer: Bake in the preheated oven for 15 minutes. Remove from the oven and reduce the temperature to 350 degrees F (175 degrees C).
5. Layer and Bake Again: Spread spaghetti sauce over the noodle mixture. Sprinkle with oregano and basil, then top with the remaining 1 1/2 cups mozzarella. Arrange pepperoni over the cheese.
6. Final Bake: Return to the oven and bake until the cheese is bubbly and beginning to brown, about 30 minutes.
7. Rest Before Cutting: Let the casserole stand for 5 minutes before cutting into it.

Note: Customize your casserole by adding your favorite vegetables or additional spices for a personal touch.