1/2 c. milk
1/3 c. sugar
4 tbsp. butter
3/4 tsp. salt
1/4 tsp. dry mustard
1/4 c. vineegar
1 egg, beaten
1 tbsp. cornstarch
3/4 tsp. celery seed
1/4 c. chopped onion
1/4 c. mayonnaise
8 boiled potatoes, skinless

Cook first 9 ingredients until thick. Remove from heat and add onion and mayonnaise. Cool. Carefully fold in potatoes. Chill.