Portabella Problems

I hate grocery shopping. The kosher supermarkets are always crowded and cramped, and I usually end up getting bumped in the rear by the shopping cart of the impatient old lady behind me. I never come prepared with a shopping list, so I just wander up and down the aisles wondering what I need to stock up on. I usually lose interest halfway through, and end up standing, sad and alone, in the middle of Aisle 5.
Enter the miracle of the phone-in order. I now call (or fax) my order in to my local supermarket, and voila, they do the shopping for me and deliver it to my door. Fantastic, right? Well, yes, except for the fact that every once in a while, the order taker misunderstands what I want, and sends me something entirely different.
I once asked for 4 kirby cucumbers, and got 4 pounds of corned beef instead. (We don't eat corned beef.) Another time, for no discernable reason, the supermarket sent me 6 bottles of diet plum juice. (We don't drink diet plum juice.)
Yesterday, I asked for a small can of button mushrooms. Instead, they sent me 6 oz. of sliced fresh portabella mushrooms. I have no idea how to cook them. Can anyone help? Please, if you have a simple recipe for portabella mushrooms, let me know, before my sanity snaps and I attack the supermarket cashier with my unwanted package of mushrooms.