MSG Smash Burgers

Ingredient:

• 1 tablespoon black pepper
• 1 tablespoon kosher salt
• 3/4 teaspoon MSG (such as Ajinomoto)
• 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 egg (optional)
• 2 tablespoons finely chopped cornichons
• 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
• 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)