I just threw this together one day and now I make it pretty frequently. It's hearty, but not heavy, so very good for a quick lunch. Crimini mushrooms are the same thing as baby portabella, you can use the big ones too and cut them up but I think the small ones are easier to deal with. If you don't have mushroom stock, you can use any good vegetable stock. This is especially good with a little grated Parmesan on top!