Old Fashioned Cooked Potato Salad Dressing

In saucepan combine:

2/3 cups sugar
1 T. flour
1/3 t. salt
1/6 t. ground mustard

Stir in:

1 egg, lightly beaten

Gradually stir in:

½ cup vinegar
1/3 cup water

Bring to a boil over medium heat, stirring
Constantly; cook and stir for 2 minutes.
Cover & refrigerate.

Before serving, add to equal amount of mayonnaise.