Step 1: Prepare the Baconnaise
1. Mix Ingredients: In a small bowl, combine the mayonnaise, chopped bacon, garlic powder, smoked paprika, salt, and pepper. Mix until well combined.
2. Chill: Cover and refrigerate the baconnaise until ready to use.

Step 2: Prepare the Smash Burgers
1. Preheat Grill or Skillet: Heat a cast-iron skillet or griddle over medium-high heat. If using a grill, preheat it to high.
2. Form the Patties: Divide the ground beef into 4 equal portions (about 4 ounces each) and gently form them into loose balls. Do not overwork the meat.
3. Season the Patties: Season each ball of meat with salt and pepper.

Step 3: Cook the Burgers
1. Smash the Patties: Place the meat balls onto the hot skillet or grill. Using a heavy spatula or a burger press, smash each ball down to about 1/2 inch thick. Cook for about 2-3 minutes until a nice crust forms.
2. Flip and Add Cheese: Flip the burgers and immediately place a slice of cheese on each patty. Cook for another 1-2 minutes, or until the cheese is melted and the burger is cooked to your desired doneness (internal temperature of 160°F for medium).
3. Toast the Buns: While the burgers are cooking, place the burger buns on the grill or in a separate pan to toast lightly.

Step 4: Assemble the Burgers
1. Spread Baconnaise: Generously spread the baconnaise on the bottom half of each toasted bun.
2. Add Burgers: Place the cooked smash burger on top of the baconnaise.
3. Add Toppings: Top with lettuce, tomato, pickles, and onion as desired. Finish with the top half of the bun.

Step 5: Serve
1. Enjoy: Serve the smash burgers immediately with your favorite sides like fries or a salad.