In the Fix 'N Mix Bowl, combine ground beef, onion soup seasoning, Worcestershire sauce and salt. Allow to marinate for at least 1h, making sure to bring it to room temperature before cooking.
In alarge fry pan, heat oil over medium-high heat. Add sliced onions, season with salt and toss to coat in oil. Add beef broth, reduce heat to low and cook for approx. 45 min., stirring occasionally, until onions are brown and caramelized.
In the last 5-10 min. of caramelizing, deglaze fry pan with balsamic vinegar. Turn off heat and remove onions into a separate container. Allow fry pan to cool then clean thoroughly.
Evenly divide ground beef into 6 equal portions, and form into patties using the Hamburger Press.
Place a clean, large fry pan over medium heat, adding a small amount of oil if needed. Add 3 burger patties to fry pan and cook for 2-3 min.* Flip patties, cook for 1-2 min., then add sliced cheese on top, place cover on fry pan and cook for 1 min. Adjust cooking time as needed until you reach desired doneness. Remove from fry pan and repeat with remaining patties.
Remove burgers from pan and allow to rest for 5-10 min. before serving.
While burgers are resting, add mayonnaise, mustard, and grated garlic to Thatsa® Extra Mini Bowl and stir to combine.
Spread dijonnaise on burger buns, add patty, top with caramelized onions and any other desired toppings.
*Check internal temperature to find out if your burger is done to your liking! And remember to remove burgers from pan a little before desired temperature, as the internal temperature will continue to rise after cooking.