Method
Light the BBQ, and assemble your ingredients while you wait for the charcoal to get to the perfect cooking stage (coals glowing red). When the BBQ is ready, place the burgers directly on to the clean grill and cook for 3-4 minutes on each side, turning the burger when grill marks appear (ideally, use a meat thermometer to check the temperature; the burgers should be 65⁰C when cooked, with any juices running clear). When you turn the burgers, top them with the cheese slices so that they melt while the burgers finish cooking. You can also toast the brioche halves at this point if you like (keep an eye on them, they won’t need long); when they’re done, transfer them to four serving plates and spread the bottom half of each bun with the mustard, then sprinkle chopped onion over the mustard. When you’re happy the burgers are properly cooked through and the cheese has melted, place a burger on top of each mustard-spread bun, top with gherkins or your favourite pickles, then spread the top half of each bun with the ketchup before pressing them down gently on top of the burgers. Enjoy!