Chicken Mushroom Casserole

2 cups cooked cubed chicken
1 - 4 ounce can mushrooms, drained
1 can cream of chicken soup
1 can cream of mushroom soup
2 cups sour cream
1/2 cup butter
7 ounces cooked spaghetti
1 cup parmesan cheese

Melt butter over low heat. Add both soups and mushrooms. Mix thoroughly. Add sour cream and mix well. Add chicken and spaghetti. Pour into casserole dish. Sprinkle cheese over the top. Bake at 350 degrees for 45 minutes.