Combine the mayo (1/2 cup), ketchup (1 tsp), mustard (1 tbsp), pickle juice (1 tsp) and cayenne(pinch) in a bowl and mix well. Refrigerate for 30 minutes for best flavor.
Make The Burgers
Slice the tomato and tear off portions of leaf lettuce. Each burger will get 2 slices of tomato and 1 piece of shaped lettuce leaf. Tear the leaf lettuce to fit the burger bun.
Open the buns, but do not slice them in half. Leave the burger buns with the hinge attached. Brush the buns with melted butter and grill on a griddle that's has preheated to 375 degrees or medium high heat. Watch carefully so they do not burn. Look for a golden brown color to develop.
Roll the burgers into balls (4 ounces), but do not pack the burgers tightly. Place the balls of burger meat on the hot griddle and smash down to form a 4-inch patty. You can use a burger press or a weighted spatula.
Lightly salt and pepper the burger and flip after 2 minutes and 30 seconds.
Flip the burger and add American cheese (1 slice). Cook for 1 more minute.
Assemble the burger by spreading the copycat shack sauce (1 tbsp)on the top bun, followed by the leaf lettuce and then the sliced tomatoes (2 slices). Place the burger on the bottom bun with the cheese facing up and close the sandwich. Enjoy!
Notes
The burger blend is important to this copycat recipe. In the market look for a blended beef of short rib, chuck and brisket. If not available, then a generic ground beef would be OK.