Heat Oil In A Large Skillet Over Medium Heat. Saute Onions Until Soft, Then Add Mushrooms, Chicken And Garlic Powder And Stir Together. Saute 15 To 20 Minutes, Or Until Chicken Is Cooked Through And Juices Run Clear. Meanwhile, Bring A Large Pot Of Salted Water To A Boil. Add Noodles And Boil For 8 To 10 Minutes, Or Until Al Dente. Drain, Return Noodles To Pot And Set Aside. Mix Sour Cream And Soup Together In A Medium Bowl, Then Add To Chicken Mixture. Heat Through, Then Add To Noodles And Stir All Together. Season With Salt And Pepper To Taste And Serve Hot.