I'm not vegetarian, but Grand Central Bakery in Seattle/Portland had a Maitake sandwich that I loved enough to reproduce at home:

"Crisp-roasted maitake mushrooms with garlicky labneh, fresh local raab, warm Middle Eastern Spices and Mama Lil's spicy pickled peppers on a toasted Ciabatta roll."

The raab and the mushrooms (sliced into sheets) were seared crisp. I substituted harissa mixed with mayo or greek yogurt for the sauce.