1/2 c. dry mustard
1/2 c. vinegar
1 egg
1/3 c. sugar
Dash of salt
Mustard mixture
1 c. mayonnaise

In a jar, mix first two ingredients. Let set overnight. In double boiler, heat 1 egg, sugar, salt, mustard mixture. Cook over hot water, stirring constantly until mixture thickens and coats spoon. Cool. Before serving, add mayonnaise.