Copycat Big Mac

Make the burger sauce: In a medium bowl, add all sauce ingredients and whisk until smooth. Refrigerate and allow flavors to combine for 1 hour. In a separate bowl, season beef with salt and pepper and form into 8 equal balls (2 ounces each).  Press into a 4 3/4" ring mould to form a thin patty. Place diced onion into ice cold water. Leave for 10 minutes and then drain. In a large skillet over medium heat, lightly toast buns, then set aside. Add oil to pan and fry patties in two batches, cooking for 2 minutes per side, until cooked. On four of the patties, top with a slice of cheese for the final minute to allow it to melt a little. To assemble the burgers, spread some burger sauce across the bottom bun. Sprinkle over some of the onions and shredded lettuce then add one burger patty. Top with a second bottom bun, more burger sauce, onions, lettuce, and pickles. Finally, top with the second burger patty and bun top.  Serve with classic fries and a can of Coke, if desired.