The Absolute Best Way To Reheat French Onion Soup
A bowl of French onion soup is a cozy, hearty dish for a cold night, but if you're a true soup aficionado, you can enjoy it any time of year. Put simply, this dish is a blend of caramelized onions cooked with beef broth, and it usually includes two added elements: bread, in the form of crostini or croutons, and cheese (often Gruyère), which is layered on top of the soup and broiled until bubbly. If you're craving a bowl of this cold-weather staple, you can certainly make it at home, but what if you have leftovers? Reheating is easy — just place the pot of soup on the stove, let it come to a boil, and serve. As for the bread and cheese, the process is essentially the same as when you make it fresh.
Reheating this soup to its best quality also means storing it properly. For the best results, store the broth in its own separate container, then add your desired amount of cheese and bread during the reheating process.
How to properly reconstitute and store French onion soup
Boiling your leftover French onion soup is the easy part. What if you want the batch to taste like you just made it fresh? In that case, you'll need to toast your bread and broil the cheese for serving. You can certainly eat the soup without these add-ons (or even just toss in some croutons for easy plating), but if you choose to include them, then you'll want to transfer the soup to oven-safe crocks once it's boiled. Top each one with a slice of bread, then a layer of cheese that covers the bowl's circumference. Then just broil the crocks until the cheese is golden and bubbly — this should only take a few minutes.
If you want to reheat the soup but don't want to keep a close eye on it, you can also do so in a slow cooker: Just add your soup to the cooker and set it to low. With this method, the soup will warm up and remain hot enough to eat within about an hour. Only do this if the soup is coming out of the refrigerator, though — reheating anything perishable (like beef broth) in the slow cooker from frozen could leave it in the dreaded "danger zone" for too long. If exposed to temperatures between 40 and 140 degrees Fahrenheit for more than two hours, the food could begin developing bacteria, per the USDA.
The best way to store French onion soup
To ensure your French onion soup maintains its best flavor, make sure to store it in an airtight container in the refrigerator. The soup will last as long as four days in the fridge, but for an even longer shelf life, you can freeze it for up to four months. If you have the option, freeze it in single-serving containers; when you're ready to eat it again, you can simply reheat a bowl whenever you need, as opposed to reheating the whole batch.
In addition to freezing the soup, you can also freeze the bread and cheese easily. Tightly wrap the bread in plastic wrap and aluminum foil and store it in a freezer-safe bag in order to keep out as much moisture as possible. With this method, it should last about three months. Follow the same procedure to store the Gruyère; it should stay fresh for at least two months, but it may last up to six.