Mustard Sauce (not glaze)

This is from Nadine Onstot who made it for a ham dinner at SPC.

1 c. white sugar

1/2 c. yellow mustard

1/4 c. vinegar

1/2 c. water

1 T flour

1 beaten egg

1/4 c. butter

Mix sugar and flour in pan. 

 Add liquids and egg. 

 Stir. 

 Add butter.

Cook over low heat until thickened.

Store in jar in refrigerator.