First, I had over 8 cups of mushrooms cleaned. Don't soak mushrooms in water, as they will soak up alot of water and then get chewy.
Put them in a set on low crock pot. Then I added one can Progresso Recipe Starters Portabello Mushroom. I know, again with a prepared product? Yes. It was FREE with a coupon, and these are the ingredients listed below. I also added one box of low sodium beef broth, and two large onions chopped. That's it! And it was DELISH! Total cost for entire side dish was 4.50, which is alot, but I will turn the leftovers into a soup (if there are any)