Prepare the Animal Style Sauce: In a medium bowl, combine the mayonnaise, tomato ketchup, English mustard, white vinegar, granulated sugar, garlic powder, and cayenne pepper (if using). Stir everything together thoroughly until the sauce is smooth and a uniform peachy-orange colour. Cover the bowl and refrigerate for at least 15 minutes to allow the flavours to meld, creating a more cohesive taste.

Caramelise the Onions: Heat 1 tablespoon of neutral oil in a large frying pan or skillet over medium-low heat. Add the finely diced white onions to the pan. Cook slowly, stirring occasionally, for 15-20 minutes until the onions turn a rich, deep golden-brown colour and are incredibly soft and sweet, releasing a wonderfully fragrant, sweet aroma. This slow caramelisation is key to their deep flavour. Once done, remove from the pan and set aside.

Form and Season the Patties: Divide the ground beef into four equal portions. Gently form each portion into a thin patty, slightly wider than your burger buns, as they will shrink during cooking. Create a slight indentation in the centre of each patty with your thumb to prevent them from puffing up. Season both sides generously with salt and freshly ground black pepper.

Cook the Patties: Heat the remaining 1 tablespoon of neutral oil in the same frying pan or skillet over medium-high heat until it shimmers. Place the patties in the hot pan, ensuring not to overcrowd it (cook in batches if necessary). Cook for 3-4 minutes per side for a medium doneness. You'll hear a satisfying sizzle, and the patties will develop a lovely browned crust. In the last minute of cooking, place a slice of mature cheddar cheese on top of each patty, allowing it to melt and become gloriously gooey.

Toast the Buns: While the patties are cooking, lightly toast your burger buns. You can do this in a dry pan, on a griddle, or under the grill until they are lightly golden and slightly crispy to the touch, releasing a warm, comforting smell of baked bread. This prevents them from getting soggy and adds texture.

Assemble Your Burgers: Spread a generous amount of the prepared Animal Style sauce on both the top and bottom halves of each toasted bun. On the bottom bun, layer shredded lettuce, sliced tomatoes, then a cheesy patty. Top the patty with a spoonful of the sweet, caramelised onions. Finish with the top bun, pressing down gently. You'll see a beautiful stack of vibrant colours and textures, ready to be devoured!