In a skillet, melt the butter and oil together. Add the diced onion and cook on medium heat until the onion is tender. Add in salt, pepper, poultry seasoning and stir to combine. Pour in minced garlic and cook until fragrant.
Meanwhile, heat salted water for pasta per the box directions. Preheat oven to 375º F.
Into the onion/garlic mixture, add in cream of chicken soup, sour cream and diced green chilies. Slowly whisk in milk - a half cup at a time, until desired consistency.
Once mixed, stir in 2 cups of the shredded mozzarella cheese and all of the parmesan cheese and let melt. Turn the stovetop off and take off heat.
Once the pasta is cooked, drain and toss into the creamy mixture, along with the cooked chicken. Pour into a 9x13 casserole dish. Top with the remaining 1/2 cup of mozzarella.
(Optional) Breadcrumb Mixture:Pour panko breadcrumbs into melted butter and stir together with a fork. Spread on top of casserole and bake uncovered for 30-35 minutes, or until bubbly and heated through. Enjoy!