Fish Sauce Is The Secret Ingredient For Richer Flavor In French Onion Soup
There are plenty of times when you shouldn't mess with a classic, but we'll bend the rules for French onion soup. Don't get us wrong, the soup is already quite flavorful. Between its sweetly caramelized onions, savory beef broth, and cheesy toasted topping, every spoonful is just as deliciously decadent and complex as the next. However, that doesn't mean the recipe can't be improved upon. Of the many flavor enhancers that could be stirred into the soup, the ace up our sleeve is fish sauce.
Given the beefiness of French onion soup, the inclusion of a fish-forward condiment might seem odd, but you'd be surprised at what a dash can do for flavor. Since fish sauce boasts a significant amount of umami, this means that it can actually amplify the soup's savoriness. Likewise, given that umami is responsible for making our mouths water, the inclusion of the briny sauce can even work to improve our overall tasting experience of the soup.
Additionally, the fermented fish sauce imparts layers of nuanced flavors to French onion soup. Beyond its pungently fishy perfume, the sauce is salty and savory with an undertone of sweetness. As a result, it effectively compliments the meaty broth, earthy onions, and funky cheese, all while perfectly contrasting the caramelized onions. With so much to offer French onion soup, not adding it to the mix of ingredients would be a missed opportunity.
Add fish sauce to soup sparingly
Any type of fish sauce can be used to jazz up French onion soup. From patis to shottsuru to colatura di alici and even Worcestershire, each condiment delivers a burst of umami. Yet, because each sauce is made differently, their profiles range; some may be intensely briny or slightly tangy, others sort of nutty or delicately honeyed. At the end of the day, finding the right sauce to work into the recipe will be a matter of preference — what's more important is knowing how to use fish sauce properly.
One of the great things about the savory sauce is that it can deliver a huge amount of flavor even when used, modestly. Since a little goes a long way, you should aim to use about 1 teaspoon of fish sauce. The tends to be the ideal amount to keep flavors in balance without having fish sauce overwhelm the palate.
As for when to add in punchy fish sauce, do so towards the end of cooking, once soup has simmered. Despite that adding it earlier would give allow it to dissipate more fully into the broth, working it in at the last second helps preserve the soup's classic French onion flavors. Plus, it also lets fish sauce integrate into the recipe more subtly, leaving behind just a whisper of its richness. But, don't take our word for it, test it out for yourself!