In a small bowl, combine the 60g mayonnaise, 60g ketchup, 60g yellow mustard, 5g Worcestershire sauce, 1 tsp smoked paprika, the finely diced ½ dill pickle, the finely diced ¼ sweet onion and the finely grated ½ garlic clove. Stir firmly until the sauce is completely uniform and an even orange-pink, with no streaks of mustard or ketchup left. Season with a small pinch of kosher salt and freshly ground black pepper, tasting as you go, since the pickle and mustard are already salty. Cover and refrigerate while you portion and cook the beef, which gives the raw onion time to soften and the garlic time to mellow. That short chill is what turns three separate condiments into one cohesive, rounded sauce.

Divide the 680g ground beef into 8 equal portions of about 85g each, two patties per burger. Keep the beef cold and handle it as little as possible, rolling each portion into a very loose ball without packing it; the surface should look rough and craggy rather than smooth. Do not flatten the balls into patties, and do not season them yet. Set them on a parchment-lined tray in the fridge until the pan is hot, and cut 8 squares of parchment about 15cm wide for smashing. Slice the 4 dill pickles lengthwise into thin planks and pat them dry. That loose, unseasoned ball is what smashes easily into thin, ragged edges and keeps its surface dry for the sear.

Heat the oven to 90°C and set a wire rack on a baking tray inside to hold the finished stacks. Place a large cast iron skillet, ideally 30cm, over medium-high to high heat with no oil and leave it for a full 3–4 minutes, until faint wisps of smoke rise from the dry surface. If a drop of water skitters and vanishes in under a second, the pan is ready; if it sits and simmers, keep heating. Plan on 4 batches of 2 balls each, letting the pan recover for 60–90 seconds between batches if it stops smoking. That stored heat in heavy cast iron is what keeps the surface hot enough to sear when cold beef lands on it.

Place 1 beef ball in the hot skillet and immediately lay a parchment square over it. Within 5 seconds, press straight down as hard as you can with a heavy, wide, flat metal spatula or burger press, using your other hand on top for extra force, and hold for 10–15 seconds until the ball spreads into a thin patty about 12–14cm across with ragged edges, then peel away the parchment. Immediately season the exposed side of each patty with fine sea salt and black pepper. Add a second ball to the other side of the pan and smash and season it the same way. Do not press either patty again. That single fast, hard smash is what puts the entire surface of the soft beef against the iron before its proteins set.

Leave the patties completely undisturbed for 90 seconds to 2 minutes, without lifting, checking or pressing them. Watch the edges: they should turn deep brown and lacy, and the raw top should start to turn pale around the rim. Slide a thin, sharp-edged spatula under one edge; if it releases cleanly, the crust is ready, and if it sticks, give it another 20–30 seconds. Then scrape firmly under the whole patty in one decisive motion, keeping the blade flat against the iron rather than lifting tentatively. That uninterrupted contact and confident scrape are what keep the caramelised crust attached to the beef instead of left behind on the pan.

Flip each patty once, then immediately season the newly exposed side with fine sea salt and black pepper. Lay 1 slice of American cheese on each patty straight away and cook for 60 seconds more, just until the second side is set and the cheese has slumped and turned glossy. Lift one patty onto the other, both cheese-side up, to make a double stack, then move the stack to the rack in the 90°C oven. Repeat the smashing, crust and flip steps with the remaining balls, letting the pan recover between batches, until you have 4 stacks. That brief second side is what melts the cheese and finishes the thin patty without drying it out.

Without cleaning the pan, reduce the heat slightly and add the 20g of unsalted butter directly into the rendered beef fat remaining in the skillet. Once it foams, place the buns cut-side down in the buttered fat, working in 2 batches if they do not all fit, and press gently with the spatula. Toast for 60–90 seconds, until the cut surfaces are golden, slightly crisp and glossy with fat. Watch closely, since the sugar in the bun can scorch quickly at this heat; if the fat starts to smoke hard, lower the heat further. That toast in butter and beef fat is what seals the crumb against the sauce and carries the crust's savoury flavour into the bread.

Spread a quarter of the burger sauce, about 60g, over the cut side of each bottom bun. Set a double stack on each sauced base, lay the pickle planks over the top layer of cheese so they cover as much of the patty as possible, and close with the top bun. Let each burger rest for 60–90 seconds, just until the cheese has fully melted and the beef juices begin to run into the sauce. Serve straight away while the edges are still audibly crisp. That short rest is what lets the juices and sauce merge into one layer without giving the bun time to turn soggy.