romaine lettuce, tomato (sliced)any other additional garnishes
Instructions
Preheat oven to 400'F.
Balsamic Marinade
Combine all marinade ingredients in a small bowl and mix.
Clean and remove stems of mushrooms. Place the mushrooms and sliced onions in a Ziploc bag and pour the marinade over them. Let them sit in the marinade for 15 minutes.
Burgers
Once mushrooms and onions have finished marinading, remove them from the Ziploc bag and place on a foil-lined pan. Pour the marinade over the mushrooms and onions and place the pan in the oven.
Bake for 20 minutes, flipping the mushrooms and stirring the onions halfway through.
Assemble burgers by placing a mushroom cap on the bottom bun and topping it with the caramelized onions, lettuce, tomato, and any other garnishes you choose and the top of the bun.