1
Spray a small pan with the vegetable spray.
2
Place the onion in the pan and cook over low to medium heat until almost soft. Add the mushrooms and garlic and cook for another 10 to 12 minutes, or until the mushrooms have released their moisture. Use more spray if needed. Allow to cool.
3
Form the meat into 4 equal flat patties.
4
Place a quarter of the onion/mushroom mixture in the center of each burger and fold the beef over the mixture, concealing the stuffing. Sprinkle with the Worcestershire.
5
Allow to sit at room temperature 30 minutes before cooking.
6
In a small bowl, combine the mayo, ketchup, and relish.
7
Cook the burgers to your desired degree of doneness, topping with the cheese for the last 3 to 4 minutes.
8
Place each stuffed burger on the bottom of a bun. Drizzle with the sauce. Layer the tomato, onion, and lettuce on the burger and cover with the top half of the bun.
