Smash Sauce: In a small bowl, combine mayonnaise, mustard, ketchup, pickle juice, pickles and onion. Set aside in the fridge while you prepare the burgers.
Burgers: In a large bowl, combine ground beef and salt and pepper. Divide beef into 12 equal round portions, taking care to not handle the meat too much. Heat a cast iron pan on high heat over a grill. Using a smaller cast iron pan or grill press, smash the patty into a thin layer. The more rough edges, the better, which will create the signature crispy edges of the burger. Flip after 1 minute and top with American cheese. If desired, top with a fried egg and remove from heat.
Top each King’s Hawaiian roll with special sauce and desired toppings and serve.