To a bowl add olive oil, soy sauce, balsamic vinegar, garlic, rosemary black pepper and a pinch of salt. Give it a good mix and sit aside.
Prep the Mushrooms
Cut off the steam, trim the edges and scrape off the gills.
Marinade the Mushrooms
Cover with the marinade and let sit for thirty minutes to one hour.
Make the Avocado Mash
Take one avocado scope out the inside add a pinch of salt and mash. If your making ahead of time add the juice of one lime.
Heat up your grill or in this case griddle. Wipe off the garlic and rosemary and place the mushrooms on the grill.
Cook until they have gotten thinner from releasing moisture and have some char. This will take about five minutes per side. I start out with the flat side down and flip after two minutes. Then flip again after two minutes. Do this until they look good.
Take the mushrooms off the grill, place between a bun and add lots of smashed avocado.