1. Place the mince, onion, garlic, 2 tsp Dijon mustard, parsley, Worcestershire sauce, gherkin and egg yolk in a large bowl. Season and mix well. Cover and chill in the fridge for 1 hour
  2. Using wet hands, shape the mixture into 8 burgers. You can freeze them at this stage if you wish
  3. Heat a griddle pan or barbecue to hot. Brush both sides of the burgers with oil and cook for 3-4 minutes each side or until well browned and cooked
  4. Meanwhile, preheat the grill to medium hot. Top each burger with a slice of cheese and grill for 2 minutes until bubbling. Toast the burger buns until lightly golden
  5. Mix the mayonnaise with the remaining 2tsp Dijon mustard and spread over the base of each bun. Add the the salad toppings of your choice, then the burger and the other half of the bun