Ingredients:

  Amount  Measure       Ingredient -- Preparation Method
--------  ------------  --------------------------------
  1                cup  half and half
     1/2           cup  sugar
     1/2           cup  white wine vinegar
  1                     egg yolk
  2          teaspoons  dry mustard
  1           teaspoon  flour
     1/8      teaspoon  kosher salt

Preparation:

1. Combine all ingredients in the top of a double boiler and heat.

2. Whisk mixture over a medium-low flame for 60 minutes, until slightly thickened serve hot or warm.