Heat oven to 190 degrees Celsius. Fry bacon and onion in large frying pan until both begin to brown and remove from pan. In the same pan fry the potatoes for five minutes in the onion and bacon residue. Cover with stock. Put three rashers of bacon and onion back, cover and cook for 5 minutes. Transfer to casserole. Season sparingly with salt, but with pepper to taste. Lay remaining bacon on top and add any remaining stock to cover. Cover and place in in the centre of the oven for half an hour or until the potatoes have cooked and have absorbed some of the stock. Sprinkle with chopped parsley and serve.
Mr Alun Williamson, who came across the recipe on this site, recalls that Tatw Pum Munud was always made with smoked bacon, and always cooked on the top of the stove, rather than in the oven. As there is a dish called Tatw Popty which by definition is oven cooked, one can only agree that the original Tatw Pum Munud was probably cooked as Mr Williamson suggests to distinguish it from the Tatw Popty, which requires a longer cooking period. Many thanks to Mr Alun Williamson.