Chicken Spaghetti Casserole is a very easy and hearty dinner. Loaded with chicken, veggies, spaghetti, lots of cheddar cheese and baked in a mushroom sauce.
Grease a 9x13 inched baking dish or large casserole pan with butter or a drizzle of oil, set aside.
Do NOT discard the water from the pot, but remove chicken from liquid and transfer to a large bowl and shred.
In the meantime add spaghetti to the pot with water, if needed break them in half. Add a drizzle of oil, and stir. Cook per package instructions, aiming for al dente, or 1-2 minutes shy from what the package cooking time suggests, as they will be cooking in the oven as well.
To the large bowl with shredded chicken add cooked spaghetti, condensed cream of mushroom soup, sour cream, grated cheese, diced onion, garlic, sliced mushrooms, diced bell peppers, poultry seasoning, dried thyme, dried rosemary and red pepper flakes. Stir to combine.
Transfer the mixture to the prepared baking dish or casserole pan.
Sprinkle the remaining 1 1/2 cup of cheese on top. Distribute evenly.