Porta Bella are those over grown brown/Crimini mushrooms that develop a richer flavor as they size up. Very popular with the non-carnivore crowd, these are very meaty and filling and can be subbed for any mushroom use.

PREP:

Snap off the stem which can be used, minus the dirt end, for later use. Brush any dirt off of the cap with a clean cloth. I do not put water to these as the mushroom with absorb it, as opposed to the baste that is to follow.

BASTE:

Mix many glugs of olive oil in a bowl with lots of crushed garlic.
Tie fresh rosemary together with a rubber band or twist tie to form a paint brush. Rosemary grows as a border plant almost everywhere. Unless you are in the middle of the bay,  you'll stumble across a rosemary bush within a block of where you are right now.  Bang the "brush" with the back of a knife, or a mallet to nick the needles of the rosemary. This will allow the herb's oils to blend with Olive's oil. Submerge this brush in the oil/garlic mixture and set aside.
This baste should be made the night before so all the flavor meld together. (Some folks add balsamic vinegar to this. I don't because it gives the 'shroom an acidic flavor.)

BURN:

Using the rosemary brush, baste the mushroom cap and fins, and place fins up on a medium hot barby. (I also forego marinating the mushroom because it soaks up too much oil. Basting has been just fine for me.)
After three or so minutes turn it over and baste again. Leave it fins down for another 3-4 minutes and turn over to finish cooking fins up.
DO NOT let the cap burn and DO keep basting. Finishing off the cooking with the fins up, ensures that all the goody juices will stay in the mushroom and not feed the fire.
Most times I will pull the mushroom off to the side and finish cooking for 5 or so minutes. Total cooking time is about 10 or so minutes. You can tell when it is done when it softens and juices up.
  You can also broil these, but keep an eye on 'em.

SERVE: