For the best burger, go to your butcher and ask them to grind 1 3/4 lbs of chuck steak for you.
This cut has a really good balance of fat and flavorsome meat.
Divide it into 4 and, with wet hands, roll each piece into a ball, then press into flat patties roughly 5 inches wide and about 3/4 inch wider than your buns. Place on an oiled plate and chill in the fridge.
Next, finely slice the red onion, then dress in a bowl with the vinegar and a pinch of sea salt. Slice the gherkins and halve the buns.
Finely chop the lettuce and mix with the rest of the burger sauce ingredients in a bowl, then season to taste.
I like to cook only 2 burgers at a time to achieve perfection, so get two pans on the go—a large non-stick frying pan on a high heat for your burgers and another on a medium heat for the bacon.
Pat your burgers with oil and season them with salt and pepper. Put 2 burgers into the first pan, pressing down on them with a slotted spatula, then put half the bacon into the other pan.
After 1 minute, flip the burgers and brush each cooked side with a 1/2 teaspoon of mustard and a dash of Tabasco.
After another minute, flip onto the mustard side and brush again with another 1/2 teaspoon of mustard and a second dash of Tabasco on the other side. Cook for 1 more minute, by which point you can place some crispy bacon on top of each burger with a slice of cheese.
Add a tiny splash of water to the pan and place a heatproof bowl over the burgers to melt the cheese—30 seconds should do it. At the same time, toast 2 split buns in the bacon fat in the other pan until lightly golden. Repeat with the remaining 2 burgers.
To build each burger, add a quarter of the burger sauce to the bun base, then top with a cheesy bacon burger, a quarter of the onions, and gherkins. Rub the bun top with a teaspoon of ketchup, then gently press together. As the burger rests, juices will soak into the bun, so serve right away, which is great, or for an extra-naughty experience, wrap each one in parchment paper, then give it a minute to go gorgeous and sloppy.