2 tablespoons unsalted butter
2 Granny Smith apples, peeled, cored and finely chopped
1 lemon, cut in half
The sauce can be made up to 2 weeks ahead, cooled, covered, and refrigerated; reheat before using.
In a large saucepan, melt the butter over medium heat. Add the onion and sauté until tender, about 5 minutes. Add the garlic and sauté until very tender, about 3 minutes. Stir in the paprika and mustard powder.
Stir in the bourbon then the vinegar and simmer for 3 minutes. Stir in the broth, ketchup, brown sugar, chipotle chilies, Worcestershire sauce, salt, and black pepper. Add the apples and squeeze the juice from the lemon into the sauce.
Note: Chipotle chilies are very spicy. Add them to the sauce at your discretion.