Smoky Portobello mushrooms and caramelized onions are surrounded by creamy brie in this grilled brie cheese sandwich,  a gourmet grilled cheese sandwich that's packed with goodness. Move over plain old grilled cheese sandwich, because I have a  grilled cheese sandwich that tastes sooo much better.  It's packed with smoky portobello mushrooms, sweet caramelized onions, and gooey brie cheese