Make the secret sauce by combining all the secret sauce ingredients together in a bowl.
Toast the buns.
Add the ground beef and onions to a large skillet over medium heat. Cook until the meat has browned.
Once the ground beef has been browned, drain the fat, if any, and add ⅓ cup of the secret sauce, 2 slices of American cheese, Worcestershire sauce, salt, and pepper. Mix until the cheese melts and a creamy sauce covers the ground beef.
To assemble the burger, take the bottom of your toasted bun and top it with lettuce, a slice of cheese, ¼ of the sloppy joe mixture, pickles, onions, and more sauce.