1/4 c. dry mustard sauce
2 tsp. sugar
1/8 tsp. salt
1/4 c. apple cider vinegar
1 egg
1/2 c. mayonnaise

In small pan, combine all sauce ingredients (except mayonnaise). Cook over low heat, stirring constantly, until thick (about 2 minutes). Chill about 15 minutes before adding mayonnaise.