How To Give Canned French Onion Soup A Boost Of Flavor
Canned soup gets a bad rap as the kind of thing you'd only eat out of desperation, but the fact is, it makes a great base to build upon. Much in the same way that boxed cake mix can be transformed into your own homemade(ish) creation with a few mix-ins, canned French onion soup, too, only needs a little bit of tweaking to taste like something that never touched a can opener in its life.
One way to better your canned onion soup is to boost it with booze. Sherry and brandy would give your soup a little flair, or you could take a page from Julia Child's book (that being "Mastering the Art of French Cooking," bien sûr) and add both white wine and cognac. You could also use a splash of cider like they do in la belle Normandie, or go with cider vinegar for some booze-free tang.
Yet another way to brighten your soup would be by adding lemon juice or by giving it a splash of Worcestershire sauce for some umami. Fresh or dried herbs can also help elevate your French onion soup, with bay leaves, sage, and thyme all being typical additions. You may also want to add a smidgen of salt if the soup is too bland or even some sugar to better simulate the caramelized quality that those canned onions probably lack.
More substantial add-ins can truly transform your soup
If you have a little more time to tweak your soup, sauteed onions are an obvious addition. You don't need to take 45+ minutes to really caramelize them, since even a five-minute saute will soften the onions up enough to give the canned soup a hearty texture as well as an extra-oniony flavor. Perhaps the best way to boost canned French onion soup, however, is to give it a cheesy topping.
All you need to do is heat the canned soup and pour it into a bowl, then top it with a slice of toasted bread (a sturdier variety such as French bread). Cover the bread with shredded cheese — gruyere or Swiss cheese if you're going French-style, but for more of an English onion soup, cheddar would be a good choice. Whichever cheese you choose, heat it up under the broiler (even the microwave will work in a pinch) until the cheese melts, et voilà! Soupe à l'oignon gratinée de cinq minutes.