Preheat the oven to 350°F (175°C).
Cook the spaghetti until al dente according to package directions.
Drain the spaghetti and set aside.
Melt the butter in a large skillet over medium heat.
Cook the diced onion until softened.
Stir in the minced garlic and cook for 30 seconds.
Add the cream of chicken soup, chicken broth, and milk.
Stir until the sauce is smooth.
Mix in the diced tomatoes, Italian seasoning, paprika, salt, and pepper.
Add the shredded chicken and stir well.
Fold in 1½ cups cheddar cheese and all of the Parmesan cheese.
Add the cooked spaghetti and toss until evenly coated.
Transfer the mixture to a greased 9×13-inch baking dish.
Sprinkle the remaining cheddar cheese over the top.
Bake for 25–30 minutes until bubbly and golden.
Garnish with chopped parsley before serving.
