• Grease a deep-sided 9x13-inch baking pan and set aside. Preheat the oven to 350℉.
• Cook the spaghetti in a large stock pot according to the package directions to al dente. You want to cook the noodles until they are just soft on the outside but still have some toothsome texture on the inside. Once the pasta is done, drain it and run it under cold water to stop the cooking process. Place in the prepared 9x13 pan and toss with olive oil to prevent the pasta from sticking together if desired.

Homemade Tomato Cheese Sauce

• Melt the butter in a medium-sized saucepan on medium heat. Sauté the onions until soft and translucent. Add in the pancetta and sauté until heated through and sizzling. Add in the garlic and Italian seasoning and sauté until fragrant. Sprinkle the flour over the flour mixture. Cook for 2-3 minutes, stirring to ensure the flour doesn't stick.
• Slowly and rapidly whisk the chicken broth into the flour mixture, making sure to whisk to ensure that there are no lumps. Once the broth has been added, keep whisking and add in the milk. Keep cooking on medium heat, whisking, until the white sauce has thickened, around 3-4 minutes.
• Turn the heat to low and stir in the Velveeta. Stir until it's mostly melted, then add the 2 cups of grated old sharp cheddar and the sour cream. Keep stirring until the cheese sauce is smooth and creamy. Make sure that all of the different cheeses have melted completely. The cheese sauce will be thick at this point. Add only black pepper to taste, as this rarely needs salt.
• Once the cheese sauce is smooth, add the tomatoes JUICE AND ALL to the cheese sauce and mix in until combined, then stir in the chicken.
• Pour the cheese sauce over the spaghetti in the pan and stir gently to combine all of the ingredients and coat the spaghetti noodles completely with the cheese sauce. Sprinkle with the cheese for the topping and place in the oven.
• Cover the casserole with tinfoil and bake in the oven for 40 minutes until heated through and bubbling at the sides. If you want the cheese to brown, remove the foil and broil for 5-7 minutes to brown the top, watching it carefully.
• Remove and let sit for 5 minutes then serve hot.