Preheat oven to 375ºF
In large dutch oven, sauté the mushrooms in the butter and oil over medium/high heat until tender. Remove from pan and set aside. While cooking mushrooms, prepare pasta according to package instructions then drain and set aside.
Once mushrooms are removed from pot, reduce heat to medium then add cream cheese, milk, Italian season, garlic powder, salt and pepper. Whisk together until smooth then heat until bubbly and thickened. Approximately 5-10 minutes.
Add pasta to thickened sauce and toss to coat. Add half of the chicken, mushrooms and cheese. Transfer mixture to a large casserole dish. Top with remaining chicken and mushrooms then cheese.
Bake for 20-25 minutes or until browned and bubbly on top.
Serve topped with chopped fresh parsley.