Cook the pasta according to the instructions, then drain and set aside.
16 oz. thin spaghetti
Preheat the oven to 350-degrees F.
Lightly grease a 9x13 baking dish with butter or cooking spray.
In a large skillet, add the butter and diced onions. Cook until they are tender.
4 tablespoons butter, 1 small yellow onion
Add the garlic and cook 1 minute more.
3 cloves fresh garlic
Sprinkle the flour over the onions and garlic and whisk to combine.
4 tablespoons all-purpose flour
Gently add the chicken stock, whisking the whole time.
1-½ cups chicken broth
Add the cream soup and the milk. Whisk until smooth and creamy.
¾ cup milk, 1 15oz can of cream soup, or 2 cups homemade Cream Soup Substitute
Then add the shredded cheddar cheese and room temperature cream cheese into the cream sauce a little at a time, stirring in between.
4 oz. cream cheese, 1 cup shredded cheddar cheese
Add salt and pepper to taste.
kosher salt and black pepper
Fold the chicken into the sauce.
2 cups shredded chicken
Add the diced tomatoes and chilies into the sauce mixture.
1 10 oz. can diced tomatoes and green chilies
Pour the sauce over thecooked spaghetti noodles and toss to coat.
Add the mixture to the casserole dish and top with shredded mozzarella cheese.
1 cup shredded mozzarella cheese
Sprinkle with a little bit of dried basil, if you like.
1 teaspoon dried basil
Bake for 20 minutes until the cheese is melted and the top is golden brown.