Preheat your grill or skillet to medium-high heat.
In a small bowl, mix mayonnaise, ketchup, Dijon mustard, and pickle juice to create the secret sauce.
Form the ground beef into four loose balls and season generously with salt and pepper.
Place each ball on the hot grill or skillet and smash down firmly to form patties. Cook for about 3 minutes until crispy edges form.
Flip the patties and immediately top each with a slice of cheese; cook for an additional minute until melted.
Assemble burgers by spreading secret sauce on both sides of brioche buns and layering with patties and desired toppings.
