Preheat to 350F. Grease pie plate, 9x 1 1/4". Beat milk, butter, vanilla, eggs, granulated sugar and Bisquick till smooth, 30 seconds in blender on High or 1 minute with hand beater. Pour into plate. Bake till knife inserted in centre comes out clean, about 30 minutes. Cool completely. Arrange bananas slices on pie. Beat whipping cream and powdered sugar in chilled bowl till stiff; spread over top.