Scald milk in the top of a double boiler.
Mix dry ingredients together in a small bowl and stir in vinegar and egg yolks.
When smooth, stir into the scalded milk and whisk and cook until thick and smooth.
Remove from heat and stir in the butter.
Cover to prevent a film from forming and cool to lukewarm.
Taste for seasoning and add more salt, sugar, a dash of cayenne, or white pepper or a few drops of hot red-pepper sauce.
Store in a covered jar in the refrigerator until needed.