1 tbsp. butter
1 c. vinegar
2 egg yolks
1 heaping tsp. mustard
2 tsp. salt
1 heaping tsp. flour
3 tbsp. sugar
1 1/2 c. boiling water or milk

Melt butter in vinegar, beat egg yolks, add mustard and all dry ingredients. Slowly add water. Cook in a double-boiler, stirring constantly until thick. Will keep indefinitely in refrigerator. Good on salads, cabbage or potatoes.