Step 1: Prepare the Chicken: In a large skillet, heat olive oil over medium-high heat. Add the chicken pieces and cook until browned and cooked through, about 5-7 minutes. Season with salt, pepper, and Italian seasoning. Remove the chicken from the skillet and set aside.
Step 2: Saut the Aromatics: In the same skillet, add the chopped onion and cook until softened, about 3-5 minutes. Add the minced garlic and cook for an additional minute until fragrant.
Step 3: Combine the Ingredients: In a large bowl, combine the cooked chicken, sauted onion and garlic, uncooked pasta, cream of chicken soup, cream of mushroom soup, and milk. Stir well to ensure all ingredients are evenly distributed. If using frozen vegetables, add them at this stage.
Step 4: Transfer to Baking Dish: Pour the mixture into a greased 9x13 inch baking dish. Spread evenly.
Step 5: Add the Cheese: Sprinkle the cheddar cheese, mozzarella cheese, and Parmesan cheese evenly over the top of the casserole.
Step 6: Bake the Casserole: Cover the baking dish with aluminum foil and bake in a preheated oven at 375F (190C) for 25 minutes. Remove the foil and bake for an additional 10-15 minutes, or until the cheese is melted and golden brown and the pasta is cooked through.
Step 7: Rest and Serve: Remove the casserole from the oven and let it rest for 5-10 minutes before serving. This allows the sauce to thicken slightly.
Optional Tips: For a spicier kick, add a pinch of red pepper flakes to the chicken while cooking. Substitute the cream of mushroom soup with cream of celery or cream of broccoli soup for a different flavor profile. For a richer flavor, use heavy cream instead of milk.