Clean and remove stems from the mushrooms. Chop into quarters.
Prepare the marinade and toss with the mushrooms. Set aside.
Preheat a grill pan and brush with olive oil.
Meanwhile, thickly slice the mushrooms separating the layers.
Once hot, add the onions and allow to cook until tender but charred. Don't cook these too fast. They will be juicy and almost sweet.
Prepare the rice according to package instructions. I flavored mine with a squeeze of lime juice, salt and pepper. You could also opt to add cilantro here as well.
Once the onions have cooked through, remove and using the same pan, brush with a bit more oil adding the mushrooms. Cook on high heat.
Chop the tomatoes and season with salt and pepper.
You could use fresh, canned or frozen corn. Fresh is best. If you are using corn on the cob, trying grilling it brushed with a bit of the marinade for added depth of flavor.
Chop the romaine and drain & rinse the black beans.
Season everything with salt and pepper.
You can compose the bowl as we did here for presentation. I prefer to combine just before serving so the heat from the vegetables doesn't wilt the romaine.
Top with taco sauce, vegan sour cream, avocado cream and serve with corn tortillas or chips.