Begin by bringing a large pot of salted water to a boil. Add the 16 oz of uncooked spaghetti and cook according to package instructions until al dente. Drain and set aside.
In a large mixing bowl, combine the cooked spaghetti, 1 cup of milk, 2 large eggs, 1 tsp of Italian seasoning, 1 tsp of garlic salt, salt, and pepper to taste. Add 1 cup of grated parmesan cheese and mix well until everything is evenly coated.
Preheat your oven to 375°F (190°C). Grease your sheet pan with cooking spray or olive oil. Carefully spread the spaghetti mixture evenly across the sheet pan, pressing it down slightly to form a crust.
Place the sheet pan in the preheated oven and bake for about 20-25 minutes, or until the edges begin to turn golden brown.
Once the base is baked, remove it from the oven. Spread the entire jar of spaghetti sauce evenly over the spaghetti crust. Then, sprinkle 2 cups of shredded mozzarella cheese over the sauce, followed by your chosen pizza toppings.
Return the sheet pan to the oven and bake for an additional 15-20 minutes, until the cheese is melted and bubbly.
Once out of the oven, let it cool for a few minutes. Slice into squares and serve hot. Enjoy your delightful Sheet Pan Spaghetti Pizza with a fresh salad or garlic bread for a complete meal!