Mix all of the sauce ingredients together in a small bowl. Place in the refrigerator while you prepare the burgers.
Divide the ground beef into 6 equal portions and gently roll into balls. Place them in the refrigerator while you heat the skillet.
Heat a cast iron skillet or griddle over medium-high heat. Toast the buns until golden brown, then set aside.
Turn the heat to high and add the oil. Place the beef balls onto the hot skillet and immediately smash them into thin patties using a sturdy spatula.
Season with salt and cook for 2 to 3 minutes until crispy around the edges. Flip, add cheese, and cook for another 1 to 2 minutes until melted.
Spread the special sauce onto the buns. Add the burgers and your favorite toppings such as pickles, lettuce, tomatoes, onions, or extra sauce. Serve immediately.
Notes
The sauce can be made up to 3 days ahead and stored in the refrigerator.