A saucepan with a close-fitting lid, and, if a gas stove is used, an asbestos mat (price 3-1/2d. at any ironmongers) is needed for this stew. Skin the tomatoes, peel and quarter the onions, and put them into the saucepan with the nutter and shut down the lid tightly. If a gas or oil flame is used, turn it as low as possible. Put the asbestos mat over this and stand the saucepan upon it. At the end of 1 hour the onions should be gently stewing in a sea of juice. Add the potatoes now (peeled and cut in halves). Also the peas, if in season. Cook for another hour. If carrot or parsnip is the extra vegetable used, cut into quarters and put in with the onions. When done, the onions are quite soft, and the potatoes, etc., just as if they had been cooked in a steamer.
Note that the onions and tomatoes must be actually stewing when the potatoes are put in, as the latter cook in the steam arising from the former. Consequently, they should be laid on top of the onions, etc., not mixed with them. If cooked on the kitchen range, a little longer time may be needed, according to the state of the fire. Never try to cook quickly, or the juice will dry up and burn. The slow heat is the most important point.