Put butter in top of double boiler. When butter is melted, add flour to form a roux, then add wine, buttermilk and mustard. Stir until mixture comes to desired consistency. If sauce is too thick, add a little milk (or water). Season to taste.
Ingredients
2 tb Butter
2 tb Flour
1 c White wine
1 c Buttermilk
3 tb Honey mustard
Salt, pepper