In the heartiness sense; no actual beef needed or desired. I'm a sucker for caramelized onion, so FOS is a favorite soup. But I like to have a large bowl of soup, with perhaps a biscuit or some crackers, as lunch. Unless I use a great deal of cheese, I don't find FOS to be substantial enough as a whole meal. So for my latest batch, I added already-cooked beans, thinly-sliced cabbage, and dried mushrooms along with the stock and wine. The flavor is still wonderfully oniony, but the soup is more filling and arguably healthier. Perhaps this is reinventing the wheel, but I have not come across a similar recipe. I got the idea because, following my mother's habit, I always put cabbage (she used steamed, I usually go with coleslaw) into her meatloaf/meatballs, where it mellows and sweetens, tasting like onion rather than cabbage. While I was improvising, I cast around for other possible additions. I would have used some little cubes of paneer or tofu if I'd had any on hand, and then omitted the gruyere topping.