In order to avoid the baguette aspect of French onion soup, I subbed in chicken breast for the bread.
What I did: Basically, I cooked up some chicken palliards (seasoned with salt and pepper in a pan). I made my normal French onion soup recipe. After the soup was ready, I stuck bowls of it under a broiler with two palliards floating on top, topped with shredded gruyere.
Did it work? Sort of. The palliards had to be cut up with a knife and fork, which was sort of awkward to eat. But the chicken added protein to the dish, which was a nice bonus. We still missed the bread, though.