Mini Guinness Pork Burgers with Guinness BBQ Sauce

1. Whisk together BBQ sauce ingredients in a medium saucepan set on high heat. When it begins to boil, reduce heat to medium-low and simmer for 20–22 minutes, until sauce has thickened. Taste and adjust seasonings, as necessary.
2. While BBQ sauce cooks, prepare burgers. Combine ground pork, mustard, stout, garlic, egg, bread crumbs, salt and pepper in a bowl. Work with your hands until all ingredients are incorporated. Form 5 to 6 small patties. Heat cast iron skillet (or sauté pan) to medium-high heat. Add cooking spray or a little oil to pan. When hot, add patties and cook on each side about 4–5 minutes, until a nice crust is formed and pork is cooked to 145°F. When burgers are almost done on the second side, add cheese slices to each burger; allow to melt.
3. Remove patties and toast buns for 30–60 seconds each in hot pan.
4. Build burgers with desired toppings and BBQ sauce.