To make the sandwich, I bought nice size mushrooms and washed them. I brushed each side with olive oil and seasoned each side (salt, pepper, basil, Lawry's). I cooked them in an iron skillet until each side was dark brown and juicy.
I put shredded cheddar on the bottom of the bun(whole grain sandwich flat for under 100 calories!), then laid the mushroom on the cheese and topped the bun off with tomato slices, fresh avocado, and chipotle mayonnaise. yummers!
(photos taken with iPhone...so excuse quality :) )