First make the sauce. In a frying pan, cook the onion in the oil over a medium-high heat for 7–8 minutes, or until it caramelises.

Tip the onion into a bowl with the ketchup, mayo and gherkins and mix it well.

Toast the cut sides of the buns in a dry frying pan over a medium-high heat, then remove from the pan. Cook the bacon in the same pan until crispy, then remove it, too, from the pan.

Put the minced beef into a mixing bowl, season well and squeeze it with your hands to bind it. Divide it into 4 equal-sized balls. Put 4 of them into the frying pan over a high heat, then cover each with a piece of baking paper and flatten them with a metal spatula or similar.

Cook for a minute or so, then flip them over and lay a slice of cheese on each. Cook for a further minute or so, then remove from the pan.

Repeat to quickly cook the remaining 2 burgers.

Assemble the burgers: spoon burger sauce over the base of the toasted buns and fill each with 2 cheesy burgers, with the tomato slices, lettuce and crispy bacon layered through. Top with more sauce and the top of the bun. Serves with chips, if you like.