1. Prepare the Baconnaise Sauce:

1. Cook the Bacon: If using bacon slices, cook them until crispy in a skillet, then crumble and set aside. Reserve the bacon grease.
2. Make the Sauce: In a small bowl, combine the mayonnaise, bacon grease (or crumbled bacon), Dijon mustard, apple cider vinegar, garlic powder, smoked paprika, and a pinch of salt and pepper. Mix until smooth and well combined. Adjust seasoning to taste. Set aside.

2. Make the Smash Burgers:

1. Form the Patties: Divide the ground beef into 4 equal portions (about 4 oz each). Roll each portion into a ball but don’t shape it into a patty yet.
2. Heat the Skillet or Griddle: Heat a large cast-iron skillet or griddle over medium-high heat. If using a grill, make sure it’s very hot.
3. Smash the Burgers: Place each beef ball onto the hot skillet or griddle and immediately smash it down with a heavy spatula or burger press, pressing firmly to flatten it into a thin patty. Smash it quickly so it gets a nice crispy edge.
4. Season: Sprinkle each patty with salt and pepper while it cooks. Let the burger cook for about 2-3 minutes without moving it to allow the crust to form.
5. Flip: Once the patty is crispy and browned on the bottom, flip it over and cook for an additional 1-2 minutes for medium-rare, or longer if you prefer your burger more done.
6. Optional Cheese: If you’re using cheese, add a slice of cheese on top of each burger patty during the last minute of cooking to melt.

3. Assemble the Burgers:

1. Toast the Buns: While the burgers cook, toast the burger buns lightly on the grill or in a skillet until golden brown.
2. Add Baconnaise: Spread a generous amount of Baconnaise Sauce on the bottom half of each bun.
3. Assemble: Place the cooked smash patty on the bun. Top with caramelized onions (if using), lettuce, tomato, pickles, or any additional toppings you like. Spread more Baconnaise Sauce on the top bun, then close the burger.

4. Serve:

• Serve the Smash Burgers with your favorite sides like fries, potato chips, or a salad!