In a small saucepan over medium heat, reduce wine, vinegar, veal stock, lemon juice and shallots. When almost all liquid has evaporated, add cream. Allow cream to reduce by half. Reduce heat slightly and incorporate the butter a few pieces at a time. Stir constantly using a wire whisk until butter is completely melted. When all butter is incorporated, remove from heat. Strain and hold in a warm (not hot) area until needed.
Yield: 2 cups