The Fonz Bacon Double Cheeseburger | The Meat Up Grill | Chef Michael Fiore

For the sauce, whisk all ingredients in a bowl until smooth. Pour into an airtight container and refrigerate until ready to use.

For the burger, preheat a griddle or cast-iron skillet over medium-high heat for about 15 minutes.

Brush the buns with melted butter, then toast lightly on the griddle or in a toaster oven before cooking the burgers.

Portion the beef into 4 loose, equal-sized balls. Arrange on the griddle or skillet 2 to 3 inches apart, then lay a piece of wax paper or parchment on top and smash the meat using a metal spatula until about ¼-inch-thick. Remove the paper and repeat with each ball.

Once patties are flat, season generously with salt and pepper. Lay the sliced onions on top to cover the patties, season with more salt and pepper.

The patties will brown around the edges after about 1½ minutes. Using the same spatula, scrape the patty off the griddle surface, making sure all the seared meat is connected to the burger and not left on the griddle, then carefully flip each patty onto the onions, which are now cooking underneath. Cook for about 1 minute, then top each patty with a slice of cheese.

Drizzle sherry vinegar around the patties so it steams and sizzles, then quickly cover with a lid to melt the cheese and infuse the sherry vinegar flavor into the meat, about 20 seconds. Uncover, then top each patty with 2 bacon slices.

Using the spatula, scrape one patty onto another, creating a double-stack, then transfer each stack onto the bottom half of each potato bun. Drizzle the M.U.G. Burger Sauce over each double-stack, then top with pickles and the bun tops.