SALAD DRESSING (for potato salad) (1973)

1 egg - 1/2 cup vinegar - 1/2 cup water - 1/2 cup sugar - 1 tablespoon flour - dash of salt - 2 tablespoon mayonnaise - 1 tablespoon mustard. Beat egg in saucepan add sugar and flour and beat together until smooth. Add vinegar and water, mix together. Cook over medium heat until thiekens, stir often. Take from heat and add mayonnaise and mustard. Beat until smooth