Salad Dressing

First part: 1 cup water, 1/4 cup vinegar. Second part: 4 tablespoonfuls flour, 2 tablespoonfuls oil; rub to paste. Add first part gradually; cook 5 minutes. Pour this mixture over well-beaten yolk of 2 eggs, stirring constantly. Chill, stirring frequently. When cold add 1 cup oil, 1/4 at a time. Add a little cayenne, 1/2 teaspoonful mustard 1 teaspoonful salt, mixed with oil.