To make the 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, stirring occasionally.
2. Taste and adjust the seasonings, as necessary.

To make the burgers:

1. In a medium bowl, combine the ground pork, mustard, stout, garlic, salt and pepper. Work the mixture with your hands until all of the ingredients are incorporated. Form 6 small patties.
2. Heat a cast iron skillet, grill or sauté pan to medium-high heat. Coat the cooking surface with cooking spray. Once it's hot, add the pork patties and cook on each side about 4-5 minutes, until a brown crust is formed and the internal temperature of the burger reaches 145 degrees.
3. When the burgers are almost done on the second side, add the cheese slices to each burger.
4. Remove patties and toast the buns for 30-60 seconds each in the hot pan.
5. Build the burgers with desired toppings and BBQ sauce.