Mix the BBQ Pulled Pork with the BBQ Sauce and heat in a small pan over medium heat, ensuring not to burn.
To prepare the patties, sprinkle the ground beef with 1 tablespoon salt and 1 tablespoon pepper. Mix well. Divide the beef into 4 burgers to create 5-inch-wide, even burgers. Do not over mix or squish, because this will cause the burgers to be tough.
To cook the burgers, ladle the bacon fat on a hot flat top grill or in a saute pan over medium-high heat. Once the bacon fat is hot, add the burgers and cook for 4 minutes on the first side, and then flip and repeat the cooking. This should yield a medium burger. For higher cook temperature, finish in a 400 degree F oven to desired temperature. Once cooked to desired temperature, top with the BBQ pork and a slice of cheese. Allow to melt for 1 minute.
During this time, spread the butter on the buns. Then place the buttered side on the flat top or in the pan to brown the butter; this will create "sealed" bread to build the burger on.
Begin assembling the burger. Take the buns off the grill and place 1/4 cup slaw on each cooked bottom bun, then a tomato slice, 2 red onions and the burger patty. Finish with the top bun. A skewer can be placed to hold the burger together.
BBQ Pulled Pork:
To prepare the pork, preheat the oven to 275 degrees F. Then sprinkle the pork with the Cajun spice and place in a 6-inch-deep casserole or roasting dish. Next, add the stock, vinegar and vegetables. Cover with foil and place in the oven for 3 hours. Once cooked, remove the pork and allow to cool. Then pick or shred the meat.
In a bowl, whisk together the ketchup, mustard, Worcestershire sauce, sugar, vinegar and spice. Then, in a small saucepan over low heat, cook for 10 to 12 minutes to blend the flavors, stirring throughout. Once cooked, remove from the heat and hold. The BBQ sauce yields 2 cups.