2 egg yolks
1 c. milk
1 tbsp. flour
1 tbsp. dry mustard
3/4 c. sugar
1/2 c. vinegar

Beat together egg yolks and milk in double boiler. Add flour, mustard, and sugar. Cook over hot water until thickened, gradually stir in vinegar. Heat thoroughly. Makes 1 1/2 cups of sauce. Keep in refrigerator. Cook over low-medium heat, stirring constantly to avoid sticking.