Each mushroom remove the stems. Wash them, and then dry them with a paper towel. Place them all in a large lasagna dish.
In a small mixing bowl mix in all the liquid ingredients Balsamic vinegar, Olive Oil, and Tamari. Then add in all other spices of onion, paprika, cumin, smoked paprika, and black pepper. Then add in the crushed Garlic and whisk well together. Brush this mix over tops of each mushroom top and bottom. Flip back over so the lid is facing up. Cover dish with plastic wrap and let sit on the counter for 30min - 1 hour.
Alternative to the ingredients, simply use your favourite BBQ Sauce and brush on all sides generously. Let sit for 30 minutes.
Heat BBQ or grilling pan on stove at medium heat. If using the pan, use the additional 2 tbsp of Olive oil. Turn down the heat to medium low, then add the mushrooms top side down so you make some nice grill marks. Depending on their size, cook approximately 3 - 5 minutes per side. I find the smaller only 3 minutes per side, and large at 5 minutes per side. Flip them over using tongs,
Remove from heat and keep covered until ready to serve.