This recipe is from Food and Drink magazine, and it's really delicious! Comments from the magazine:
Elegant French onion soup becomes hip with this gooey grilled-cheese "sannich" Australian slang for sandwich;slid into the bowl. For onions, choose sweet varieties such as large Spanish or red, as they caramelize well. And if Swiss cheeses are not favourites, medium or old cheddar is a delicious stand-in. Be warned, most purchased broths are quite salty, so season only after the soup is finished.