The world of the vegetarian sandwich is a cold, desolate one. It seems to me that practcally every sandwich out there involves some sort of meat, and those that don't are composed mostly of lettuce. This is my effort to absolve this travesty of the sandwich universe. This isn't really a recipe, so I'm just going to give it to you straight.
Fill a pan with a little bit of olive oil or Canola oil. Oh, and make sure your stove is nice and dirty and your camera is broken, or this sandwich will be ruined. JUST KIDDING, ha ha, I'm not bitter. Slice up an onion by first cutting it in half to remove the outer papery layer, then resting it on its flat side and cutting down its length. Throw as much onion as you want into the pot; for one sandwich, a quarter of an onion will more than suffice, usually. Let the onion sizzle for a few minutes, depending on how soft you like your sauteed onions. I like mine nice and soft and brown and caramelized, which is why I put them in a good three or four minutes before the mushrooms.By now the onions and mushrooms should be ready. They will have cooked down quite a lot: The onions will be brown and translucent, and the mushrooms will be a deep sienna.

Would you just look at that? Some people would look at this gem of nature and think: "Jam! Cookies! Cobbler!"
