Gently combine the ground beef in a bowl, just until loosely mixed. Avoid overworking the meat to keep the burger tender.
Divide the beef into four equal portions and shape each into a patty about ¾ inch thick. Make a slight indentation in the center of each to prevent bulging during cooking.
Preheat your grill or cast-iron skillet over medium-high heat until hot and slightly shimmering, ready to sear.
Place the patties onto the hot surface, listening for a satisfying sizzle. Cook for about 4 minutes on one side until deep caramelized crust forms.
Flip the patties using a spatula, then immediately top each with a slice of cheddar cheese. Continue cooking for another 4 minutes, until the cheese melts and the internal temperature reaches 71°C (160°F).
While the patties cook, lightly toast the brioche buns on the grill or in a pan for about 1 minute until golden and crispy.
Slice the onion thinly if using, and prepare pickles and condiments for assembly.
Assemble each burger by placing a cheese-topped patty on the toasted bun bottom, layering pickles, onions, and condiments, then topping with the bun lid.
Serve immediately, with the crispy, smoky crust, juicy interior, and vibrant toppings ready to enjoy.
