Jewish string beans with tomatoes

Cut off both ends of the beans, string them carefully and break into pieces about an inch in length and boil in salt water. When tender drain off this brine and add fresh water (boiling from the kettle). Add a piece of butter, three or four large potatoes cut into squares, also four large tomatoes, cut up, and season with salt and pepper. Melt one tablespoon of butter in a spider, stir into it one tablespoon of flour,
thin with milk, and add this to the beans.