Preheat oven 400F. Heat butter and oil in large fry pan. Toss in mushrooms and cook over medium-high heat for 4 to 5 minutes. Season. Spread mushrooms, green onions, cheese and tarragon in bottom of greased 10 inch pie plate. Beat remaining ingredients 15 seconds in blender or 1 minute with hand beater till smooth and pour over vegetable mixture. Bake in preheated 400F oven for 30 to 35 minutes or till top is golden and pie is cooked. Let stand 5 minutes before serving. Garnish with tomato and parsley.