Heat oven to 350^. Grease a 9-inch pie plate. Beat milk, margarine, vanilla, eggs, sugar and baking mix until smooth, 30 seconds in blender on high or 1 minute with hand beater. Pour into buttered plate. Bake until knife inserted in center comes out clean, about 30 minutes. Cool completely. Arrange banana slices on pie. Beat whipping cream and powdered sugar in chilled bowl until stiff; spread on top. Thawed whipped topping can be used instead, if desired.