1 tbsp. flour
2 tbsp. sugar
1/2 tsp. dry mustard
1/2 tsp. salt
1/4 c. water
1/4 c. cider vinegar
1 tbsp. butter
2 egg yolks, slightly beaten
1 c. dairy sour cream

Combine the first 4 ingredients in a saucepan; mix well. Gradually blend in a mixture of water and vinegar; add the butter. Cook over low heat stirring constantly until mixture boils and thickens; cook 2 minutes.

Vigorously stir about 1/4 cup of the hot mixture into egg yolks; quickly blend into hot mixture. Continue cooking over low heat until egg thickens, about 5 minutes; stir constantly.