What You Need
Make the sauce: In a medium bowl, combine the mayonnaise, ketchup, relish vinegar, and mustard; set aside.
Make the smash burgers: Shape the ground beef into eight 3-ounce balls.Heat the HexClad Hybrid Double Burner Griddle over medium-high until very hot, about 2 minutes; lightly brush the griddle lightly with vegetable oil. Add the buns, cut side down. Cook until lightly toasted, about 1 minute. Remove buns to a plate.
Wipe the griddle clean and evenly space the balls on the griddle, smashing them flat with a spatula as you place them down to form patties at least 4-inches wide. Season patties with salt and pepper. Cook, until golden on bottom, 1 to 2 minutes. Flip each patty and cook 30 seconds more. Arrange cheese on top of half of the patties and continue to cook until cheese is melted and patties are medium, about 1 minute more. Stack patties without cheese on top of patties with cheese.
Spread bottom buns with sauce and top with lettuce and tomato. Arrange patties on top of the bottom bun and top with pickles. Sandwich with top bun and serve.