In a 3 quart suacepan, brown feef, half at a time, in melted shortening. Sprinkle with a little salt. Add the 2 cups of water, mustard and seasoned salt. Simmer covered for between 1 hour and 1 and one half hours or until meat is almost tender. Add onions and carrots and cook 30 minutes more or until vegetables are tender. Stir the 1/3 cup of water into the cornstarch and add to the stew. Cook and stir until the mixture is thickened and bubbly. Cook 1 minute more.