Put tinly sliced potatoes in a well greased 2 litre casserole. Add 1 cup milk, sprinkle with salt and pepper. Combine remaining quarter cup milk with bread crumbs, seasonings, butter and onions. Spread over top of potaotes. Cut tenderloin into 1 cm slices, pound flat. Place on top of bread dressing. Dot with butter. Cover and bake at 180ºC . for 1.5 hours. Serves 4.