Ingredients:

For the Sauce:

• 1/2 cup mayonnaise
• 2 tablespoons Kewpie mayonnaise (Japanese-style, if available)
• 2 tablespoons ketchup
• 1 tablespoon Dijon mustard or yellow mustard
• 1 tablespoon Worcestershire sauce
• 2 tablespoons finely chopped pickles or pickle relish

For the Caramelized Onions:

• 2 large onions, thinly sliced
• 2 tablespoons butter
• Salt and pepper to taste

For the Patties:

• 1 pound ground beef (preferably 80% lean, 20% fat)
• Salt and pepper to season

To Assemble:

• Potato or Brioche buns, lightly toasted
• Sliced cheese (optional)
• Lettuce, tomato slices, and any other desired toppings

Instructions:

1. Prepare the Sauce:
• In a small bowl, combine the mayonnaise, Kewpie mayo, ketchup, mustard, Worcestershire sauce, and chopped pickles. Mix well and set aside or refrigerate until ready to use.
2. Caramelize the Onions:
• In a large skillet, melt the butter over medium heat.
• Add the thinly sliced onions and cook, stirring occasionally, for about 30 minutes or until the onions are golden brown and caramelized.
• Season with salt and pepper to taste. Remove from heat and set aside.
3. Forming the Patties:
• Divide the ground beef into equal-sized portions, about 4 to 6 ounces each.
• Gently form each portion into a loose ball without compacting the meat too much.
4. Cooking the Patties:
• Heat a large skillet or griddle over medium-high heat until very hot.
• Place each ball of ground beef onto the hot surface, leaving plenty of space between each one.
• Immediately press down firmly with a spatula to smash each ball into a thin patty, about 1/4 inch thick. Pressing down helps create crispy edges.
• Season the top side of each patty with salt and pepper.
• Cook each patty for about 2-3 minutes without moving them, allowing a crust to form on the bottom.
• Flip each patty and cook for an additional 1-2 minutes for medium doneness or longer if desired. Add cheese slices during the last minute of cooking, if using.
5. Assemble the Burgers:
• Spread a generous amount of the prepared sauce on the bottom half of each toasted bun.
• Place a cooked patty on top of the sauce.
• Add a spoonful of caramelized onions on top of each patty.
• Add lettuce, tomato slices, or any other desired toppings.
• Close the burgers with the top halves of the toasted buns.
6. Serve and Enjoy:
• Serve the smashed burgers immediately while warm and enjoy the delicious blend of flavors!

Tips:

• Make sure your patties are larger than your buns initially, as they will shrink when cooked.
• Use a heavy-duty spatula to press down firmly when smashing the patties to achieve that crispy, caramelized crust.
• Experiment with different cheese options such as American, cheddar, or Swiss for added flavor.