In a small bowl, whisk together all of the ingredients for the sauce. Set aside.
Preheat a gas or charcoal grill to medium-high heat. Divide the meat into four equal portions and shape them into burgers about 3/4-inch thick. Liberally season the outside of each burger with salt and pepper, then cook them to your liking, about 3 minutes per side for medium, placing two slices of cheese on each burger once they've been flipped.
Serve the burgers on the buns with whatever garnishes you desire and a hearty dollop of secret sauce.