I am hosting a barbecue next weekend with the main attraction being a long-smoked brisket. I have a couple of very good friends who are vegetarian. While I'm going to have a lot of sides, like pasta salads, baked beans, etc., I wanted to serve something to them that doesn't seem like an afterthought. I was thinking of smoking some portobello mushrooms with a nice stuffing of breadcrumbs and fontina. They are sick of tofu. Any suggestions?