Steps 
1. For the burger sauce, whisk the sauce ingredients together and store in the fridge until needed.

2. Divide ground beef into 4 thin patties. They should be thin, so they cook quickly.

3. In a large skillet or on a griddle over medium-high heat, add a drizzle of neutral oil and add the beef patties. Press down on patties gently, so they form a crust on the bottom. Cook for about 3 minutes. Season patties with salt and pepper.

4. Flip patties and cook for another 2-3 minutes to finish cooking patties. Top each patty with American cheese and cheddar.

5. To assemble burgers, toast the buns and smear a big spoonful of burger sauce on the bottom bun. Top with tomato, lettuce, one cheese slice, a slice of onion, a second patty, and the bun topper.