Favored in the Midlands of South Carolina, Mustard based barbecue sauces have their origins in the 18th century when German immigrants brought this style of sauce from Europe and combined it with the indigenous pork barbecue. To this day you can still see the German connection in the names of the towns and BBQ joints where mustard sauce is still the only way to go.
Mustard barbecue sauces have a tangy flavor that is usually offset by sweet in the form of molasses or brown sugar. Often these mustard sauces are heated up with hot sauce which is typical of all Carolina barbecue sauces. Of course you can choose between the heat and the sweet as long as you keep the mustard at the heat of the sauce.
Some mustard barbecue sauces contain beer. This is a throwback to those German roots. While any beer will do I suggest you pick one that is not overly bitter and that you let it go flat before combining it with the sauce.
Like many barbecue sauces, mustard sauces should be allowed to combine before you serve it. Many of these sauces are cooked first, but the real secret is to give the sauce time for the flavors to mix. Therefore, it is best if you make up your mustard barbecue sauce a day or two before you intend to serve it. You really will notice the difference.