Cut the potatoes into quarters. Cut the turnip to the same size. Boil the potatoes and turnips together for 20 minutes then drain.
Cut the cabbage into 2 inch pieces and steam for about 8 minutes. While this is steaming, mash the potaotes, turnips, milk and butter together. Season to taste.
Finally drain the cabbage, add to the mash, stir well in and serve with roast or boiled meat.