Mop Sauce

Add the onions and 1 1/2 cups water to a saucepan. Bring the water to a boil over high heat and cook the onions for 20 minutes. Add the butter, Worcestershire sauce, white wine vinegar and mustard flour. Reduce the heat to medium low and cook until the sauce thickens, about 45 minutes. NotesThis recipe was provided by a chef, restaurant or culinary professional and may have been scaled down from a bulk recipe. The Food Network Kitchens have not tested it for home use and therefore cannot make any representation as to the results.