POTATOES AND MUSHROOM STEW

1-1/2 lbs. of potatoes, 1 Spanish onion, 1/2 lb. of mushrooms, 1 oz. of butter, pepper and salt, and 1 teaspoonful of Allinson cornflour for thickening. Peel, wash, and cut into pieces the potatoes; chop up the onion, and set both over the fire with 1 pint of water, the butter and seasoning; let cook until the potatoes are about half done. Meanwhile skin, wash, and cut into pieces the mushrooms, add them to the other ingredients, and let all stew together until tender. Thicken the liquid with the cornflour, boil up, and serve.