French Onion Soup Portobello Burger

So I know what you’re thinking. Soup-burger? It really makes no sense, but it will. Allow me to explain. I love french onion soup. It’s one of the unhealthiest of all soups, there’s tons of cheese, buttery-sauteed onions and a whole bunch of bouillon. It’s delicious for those reasons. I also love mushrooms. While there’s…