Make the Sauce: In a small bowl, combine the mayonnaise, ketchup, American mustard, chopped gherkins, smoked paprika, and garlic powder. Stir until everything is well mixed. Set aside. You can do this a day ahead to let the flavours meld.

Prep Your Toppings: Halve your brioche buns. Slice the onion as thinly as you possibly can. Have your cheese slices and gherkins ready and within easy reach of the stove.

Portion the Mince: Gently divide the beef mince into four equal 125g portions. Loosely roll each portion into a ball. It's important not to compact the meat too much at this stage – just shape it enough to hold together.

Heat Your Pan: Place a large cast-iron skillet, heavy-based frying pan, or flat-top griddle over a high heat. Add the oil and let it get incredibly hot. You're looking for it to be shimmering and almost smoking. This intense heat is non-negotiable for a good crust.

Toast the Buns: Place the brioche buns, cut-side down, onto the hot pan. Toast for 30-60 seconds until they are golden brown and slightly crisp. Remove them and set them aside.

Smash the Burgers: Place two of the mince balls onto the hot skillet, leaving plenty of space between them. Immediately, place a small square of baking parchment on top of one ball and press down firmly with a large, sturdy metal spatula for about 10 seconds, until the patty is very thin (about 1cm). Peel off the parchment and repeat with the second ball. What works best for me is using a second spatula to apply extra pressure on the first one for a really good smash.

Season and Cook: Season the tops of the smashed patties generously with salt and pepper. Cook for 60-90 seconds. You’ll see the edges turning dark brown and crispy.

Flip and Add Cheese: Using your spatula, carefully scrape under the patties to ensure you get all the flavourful crust, and flip them over. Immediately place a slice of cheese on top of each patty. Cook for another 60 seconds until the cheese is perfectly melted and the burger is cooked through.

Assemble: Spread a generous layer of burger sauce on the top and bottom toasted buns. Place a cheesy patty on each bottom bun, top with sliced onion and gherkins, and finish with the top bun. Serve immediately.