Preheat your oven to 350°F (175°C). Grease a 9×13-inch baking dish.
2. Cook the Spaghetti
Bring a large pot of salted water to a boil. Add the spaghetti and cook according to the package instructions until al dente. Drain and set aside.
3. Sauté the Onion and Garlic
In a large skillet, heat the olive oil over medium heat. Add the diced onion and sauté for 3-4 minutes until soft.
Add the minced garlic and cook for another minute until fragrant.
4. Make the Sauce
In the skillet with the onions and garlic, add the cream of mushroom soup, cream of chicken soup, diced tomatoes with green chilies, and chicken broth. Stir until well combined.
Add the shredded cheddar and mozzarella cheese, stirring until melted and smooth. Season with garlic powder, onion powder, salt, and pepper to taste.
5. Combine the Chicken and Spaghetti
Add the cooked, shredded chicken and the cooked spaghetti to the sauce. Toss everything together until the pasta and chicken are well coated with the cheesy sauce.
6. Bake the Casserole
Transfer the chicken spaghetti mixture to the prepared baking dish. Top with additional shredded cheddar cheese for an extra cheesy finish.
Bake in the preheated oven for 20-25 minutes, or until the cheese is melted and bubbly.
7. Serve
Garnish with fresh parsley if desired, and serve hot.
