Smash burgers

Method

1. To make the sauce, mix together all the ingredients apart from the gherkin brine. Then add enough brine to loosen the sauce (but not so much it becomes runny). Taste and add more salt, sugar or brine to taste.
2. Put a wide cast-iron or stainless steel frying pan over a medium heat and wait  for it to heat up. Meanwhile, divide the mince into 4 equal balls. Flatten the balls slightly to make them into thick pucks.
3. Put the pucks in the frying pan, spaced out as far as possible. Use 2 frying pans or work in batches if needed. Using a metal spatula and a rolling pin (or a metal press, if you have one), smash the pucks into thin patties, pressing down hard and getting them as thin as possible. Season liberally with salt and pepper and cook for 2 minutes, pressing the patties back down if they start to rise in the centre.
4. Use a metal spatula to scrape the patties off the pan and flip them, season with a touch more salt and lots more pepper, then lay a slice of cheese on top of each one. Cook for another 2 minutes, then scrape them up and set aside.
5. Spread both cut sides of the buns with the sauce, then put 2 patties on each bun base, cheese-side up. Top with the sliced gherkin, put the lid on top and wrap the burgers in foil. Leave for a few minutes, then unwrap and enjoy.