Ingredients :

Burger Salt :

• 1 tablespoon black pepper


• 1 tablespoon kosher salt


• 3/4 teaspoon MSG (such as Ajinomoto)

Special Sauce :

• 1 cup mayonnaise


• 1 garlic clove, grated


• 1 teaspoon sherry vinegar


• 3/4 teaspoon smoked paprika


• 1/2 teaspoon yellow mustard


• 1/4 teaspoon kosher salt


• 1/4 teaspoon MSG (such as Ajinomoto)


• 1 soft-boiled large egg (optional)


• 2 tablespoons finely chopped cornichons

Soubise Onions :

• 1 yellow onion, thinly sliced (about 2 1/2 cups)


• 2 teaspoons granulated sugar


• 2 teaspoons kosher salt


1/2 cup unsalted butter (4 ounces), cut into 1-inch cubes

Smash Burger :

• 2 pounds burger blend ground beef (such as ground chuck and brisket)


• Cooking spray


• 8 slices American cheese


• 4 sesame seed hamburger buns, split and toasted


• 1/2 cup sliced half-sour pickles (such as Ba-Tampte)




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Directions :

1. Stir together black pepper, kosher salt, and MSG in a small bowl;
   
   set aside.




2. Combine mayonnaise, garlic, vinegar, paprika, mustard, kosher
   
   salt, MSG, and egg, if using, in a blender. Process until smooth,
   
   about 1 minute. Transfer mixture to a medium bowl; stir in
   
   cornichons. Cover and refrigerate until ready to use.




3. Toss together onions, sugar, and salt in a medium saucepan to
   
   coat. Let stand at room temperature 30 minutes. Add butter, and
   
   cook over medium, stirring occasionally, until onions are softened
   
   and translucent but not browned, 25 to 30 minutes. Remove from
   
   heat, and set aside.




4. Shape meat into 8 (4-ounce) balls (about 1/2 cup each). Heat a
   
   large cast-iron skillet or griddle over medium-high. Working in
   
   batches, place meat balls in skillet, spacing at least 3 inches apart.
   
   Lightly coat the back of a heavy metal spatula with cooking spray,
   
   and smash each ball to flatten to about 1/3-inch thickness.
   
   (Alternatively, place a small sheet of parchment paper on each
   
   meat ball, and smash using a cast-iron burger press; remove
   
   parchment.) Sprinkle top of each flattened patty with 1/4 teaspoon
   
   reserved burger salt. Cook until bottoms are browned and lightly
   
   crisp, about 2 minutes. Flip patties, and sprinkle each with 1/4
   
   teaspoon burger salt. Reserve remaining burger salt for another
   
   use. Top each patty with 1 cheese slice. Cook until cheese is
   
   melted and patties are cooked through, about 2 minutes.




5. Place 2 tablespoons reserved soubise onions on each bottom bun.
   
   Top each with 2 patties, 1 1/2 tablespoons special sauce, and 4 to 5
   
   pickle slices. Cover with top buns. Reserve remaining soubise
   
   onions and special sauce for another use (see Note). Serve
   
   immediately.