Ultimate Smash Burgers with Creamy Sauce

Method

1. Divide the ground beef into 4 equal portions (about 3 oz / 85g each). Roll each portion into a ball.
2. Place each ball between two pieces of parchment paper. Using the flat side of a meat mallet or a heavy pan, press each ball into a thin, even round patty.
3. In a small bowl, whisk together the mayonnaise, sour cream, ketchup, mustard, and black pepper until smooth. Cover and refrigerate until needed.
4. Heat a large cast iron skillet or griddle over medium-high heat until very hot, almost smoking.
5. Season one side of each patty generously with salt and pepper. Place the seasoned side down onto the hot pan. Immediately season the other side with salt and pepper.
6. Cook for 1-2 minutes, until the edges are browned and crispy. Flip the patties. Cook for another 30 seconds to 1 minute. Place a slice of cheddar on one patty, then stack the second patty on top. Remove from the pan.
7. Toast the brioche buns cut-side down in the same pan for about 30 seconds, until lightly golden. Transfer to a plate.
8. Spread a generous spoonful of the sauce on the bottom bun. Top with lettuce, tomato slices, and onion. Place the double patty stack on top. Add pickles, more sauce, and finally the top bun. Serve immediately.