Put your sliced onions and balsamic vinegar in a large skillet with a tight fitting lid.
If you don’t have one you can use a pot instead, but the process may take a bit longer.
Cover and cook over medium heat for about 20 minutes.
Take off the lid and continue to cook, stirring every few minutes, until there
is no liquid left.
Once this happens, the onions will start to caramelize. You’ll then add 1/3 cup of water, stirring again until there is no liquid left.
Repeat this process until the onions are fully cooked and caramelized. Set aside.
Heat 30ml of oil on high in a non-stick pan.
Add the defrosted Big Fry Burgers and reduce to medium heat.
Fry for 9 minutes, turning occasionally.
Add the vegan cheese slices then allow them to melt slightly.
Add the burgers to buns, top with the balsamic caramelized onions and the top of the burgers. Enjoy!