In a small bowl, combine the mayonnaise, ketchup, yellow mustard, Worcestershire sauce, smoked paprika, finely diced pickle, finely diced onion, and grated garlic. Stir firmly until completely uniform — no visible streaks of individual ingredients should remain. The smoked paprika disperses into the fat of the mayonnaise as you mix, tinting the sauce a warm, deep orange-pink that is visually characteristic of a proper burger sauce. The sauce is built on a three-condiment base — mayo, ketchup, and mustard — that covers all three primary flavour registers simultaneously: richness from the mayo, sweetness and acidity from the ketchup, and sharp, fermented tang from the mustard. Worcestershire sauce adds the umami depth that the three condiments lack individually. Diced pickle provides briny punctuation and textural contrast. Finely diced sweet onion adds mild sweetness and crunch. Grated garlic — on a Microplane ideally, so it dissolves into the sauce completely — provides savory backbone without any detectable garlic pieces. Season with a small amount of kosher salt and freshly cracked black pepper, tasting as you go. Refrigerate until needed. This sauce is noticeably better after even 30 minutes in the refrigerator as the raw onion softens in the acid, the garlic mellows, and all components integrate into a cohesive sauce rather than tasting like individual ingredients combined.

Divide the 680g of ground beef into 8 equal portions of approximately 85g each — two patties per burger, four burgers total. Handle the beef as minimally as possible. Roll each portion into a very loose ball shape without compacting it — the looser the ball, the more easily it smashes flat without resistance, and the more irregular and craggily textured the smashed patty's edges will be. Irregular, craggy edges produce dramatically more surface area in contact with the hot pan, which means more Maillard browning, more crust, and more flavour than a smooth, evenly compacted ball produces. Do not form flat patties — the smashing technique requires a ball shape. Season the tops of the balls lightly with kosher salt and black pepper immediately before cooking — the seasoning goes on just before they hit the pan rather than in advance, because salt draws moisture to the surface and any moisture on the surface of the beef when it contacts the hot pan creates steam that inhibits the crust formation the entire technique depends on.

Place a large cast iron skillet over medium-high to high heat and allow it to preheat for a full 3–4 minutes until you see faint wisps of smoke rising from the dry surface. The temperature of the cooking surface at the moment the beef makes contact is the single most important variable in smash burger cooking — it determines the entire quality of the crust. An under-heated surface produces grey, soft, steamed beef with minimal browning even when smashed thin. A correctly preheated surface at the threshold of smoking produces the immediate, aggressive Maillard browning that creates the deeply caramelised, lacy-edged crust that defines a proper smash burger. Cast iron is the correct material for this application because its thermal mass retains heat through the cold beef contact that would drop a thinner pan's temperature below the effective searing threshold. Work in batches of 1–2 balls at a time to maintain the pan temperature. Each batch of two balls requires the pan to be smoking hot when they go in — allow 60–90 seconds of recovery time between batches if needed.

Place one beef ball in the hot pan. Immediately place a piece of parchment paper or greaseproof paper over the ball and position a heavy, wide, flat spatula — or a dedicated burger press — directly over the centre. Apply firm, direct, downward pressure for 10–15 seconds, pressing as hard as you can, spreading the ball from its centre outward into a thin, roughly 12–14cm patty with irregular, thin, craggy edges. The smashing must happen within the first 5 seconds of the beef hitting the pan — once the proteins begin to set from the heat, the ball resists smashing and the benefit of the technique is lost. The craggy, irregular edges produced by hard smashing are not an accident or a flaw — they are the most important textural element of the technique. Those thin, irregular edges make direct contact with the pan over their entire surface, caramelising to a deep, crispy, almost lacy char that no other burger preparation technique produces. Season the top surface with an additional small amount of salt and pepper while the patty cooks. Repeat for the second ball if doing two at once.

After smashing, put the spatula down and leave the patties completely undisturbed for 90 seconds to 2 minutes. The temptation to check the underside, to press again, or to move the patty must be resisted entirely. The crust forms through sustained, uninterrupted contact between the beef and the hot pan surface — every movement disrupts this contact and resets the browning process. You will know the crust is ready to release by two indicators: the edges of the patty will show visible browning and the beef will naturally release from the pan surface when you slide a thin spatula under it. If it sticks and requires force, it needs another 20–30 seconds. When the crust has fully developed and releases cleanly, scrape firmly under the entire patty in a single decisive motion — do not lift tentatively, as tentative scraping tears the crust rather than releasing it intact.

Flip each patty onto its uncooked side. Immediately place one slice of American cheese on top of each patty. Cook for exactly 60 more seconds — the second side does not need as long as the first because it has already been partially cooked through during the smash, and the objective is only to set the second side and melt the cheese rather than to develop a full second crust. American cheese is the only correct choice for a smash burger — its emulsified fat structure melts at the low temperature produced by the residual heat of the just-flipped patty without any additional heat source required. It flows smoothly over the crust's irregular surface, coating it evenly. Natural cheeses require higher temperatures to melt and tend to separate their fat and protein rather than melting uniformly. Remove both patties. Place the first patty, cheese-side up, and immediately place the second patty directly on top of it, cheese-side up. The heat from both patties and the residual heat of the stacking causes the two cheese slices to begin to meld together slightly — this double-cheese, double-patty stack is the structural and textural heart of the double smash burger.

Without cleaning the pan, reduce the heat slightly and add a small amount of butter directly into the rendered beef fat remaining in the skillet. Place the buns cut-side down in the buttered fat and press gently with the spatula. Toast for 60–90 seconds until the cut surfaces are golden, slightly crisp, and saturated with the combined butter and beef fat from the pan. Toasting buns in the residual beef fat rather than fresh butter alone is not a minor upgrade — the beef fat carries the flavour compounds produced during the crust development directly into the bun's surface, adding a savory, caramelised depth to what would otherwise be simply a toasted, buttery bun. Watch carefully — the residual beef fat and sugar in the bun can produce dark browning quickly at this temperature.

Spread a generous amount of burger sauce on the inside face of the bottom bun. The sauce goes on the bottom rather than both buns because it needs to stay in contact with the beef — the juices running from the hot stacked patties will mix with the sauce during the brief rest, creating a combined burger-sauce-and-beef-juice layer that is the flavour foundation of every bite. Place the stacked double-patty directly onto the sauced bottom bun. Arrange the dill pickle planks — cut lengthwise into long, flat strips rather than rounds, so they cover the maximum surface area of the patty — over the cheese. Add the top bun. Allow the assembled burger to rest for 60–90 seconds before serving. During this brief rest, the cheese finishes melting fully, the sauce and beef juices begin to combine, and the steam pressure inside the burger equalises slightly. Serve immediately while the crust is still audible.