South Carolina Mustard Barbecue Sauce

Makes about a cup of sauce 
1	 tablespoon olive oil or vegetable oil 
1/4	 cup minced onion 
3	 cloves garlic, minced 
1	 cup yellow ballpark-style mustard, like French's 
1	 teaspoon dry mustard 
1/4	 cup ketchup 
2	 tablespoons sugar 
1	 teaspoon chili powder 
1 	 tablespoon Worcestershire sauce 
1	 tablespoon freshly ground pepper 
1	 tablespoon red pepper flakes 
3/4	 cup water 

 Sauté onions and garlic in olive oil on low heat until soft and transparent. 
 Whisk in remaining ingredients, cook on low heat for 30 minutes stirring often. 
 Thin sauce if necessary with additional water. 
 Add more red pepper flakes if you want it spicier. 
 Cool then refrigerate.
 
 http://food52.com/recipes/21962-giddy-swamp-south-carolina-mustard-barbecue-sauce