Peel the onions and slice them into rounds. Peel the potatoes as thinly as possible. Leave them whole unless they are very large. Cut the meat into good-sized pieces. Small chops can be left whole, larger ones divided in two. Place a layer of onions on the bottom of a heavy casserole, and the meat on top of them. Sprinkle chopped thyme and parsley generously, and season well. Layer the rest of the onions with the potatoes. Sprinkle thyme and parsley again at the last. The amount of water you need to add depends on how good the seal is between your pot and its lid, and whether you like a "wet" or "dry" stew. You will certainly not need more than two cups, and I use barely one. Bring the water to a boil, cover as tightly as possible, and place in a preheated oven at 150ºC for 2.5 3 hours. Keep an eye on it towards the end, and adjust the gravy by adding a little water if you think it too dry. A good stew should have some gravy, but should not be flooded by it. "Floury" potatoes will dissolve into the gravy, "waxy" ones will not. I tend to use a mixture. Serve very hot with more fresh chopped parsley sprinkled on top. White soda bread to mop up the gravy.