For The Richest French Onion Soup, Reach For Fish Sauce

If you're craving a cozy soup, it's hard to beat French onion. French onion soup is a hearty, salty dish with French roots that's made with beef broth, caramelized yellow onions (arguably the best onion variety of French onion soup), bread, and a topping of Gruyére. That first bite is the best part — breaking through the cheesy layer to reach that delicious broth underneath. But if you want your French onion soup to truly stand out, your broth deserves a little fish sauce.

Fish sauce is made from three main ingredients: anchovies, water, and salt. Before you run at the sound of anchovies, though, understand that in small quantities, they add a salty, savory flavor to almost anything. Fish sauce does have a hint of a fishy taste to it, but you won't notice it in the soup. Rather, you'll only relish the punch of umami flavor that comes from it. Fish sauce has a deep, rich taste, and when paired with the salty beef stock and acidic sherry, it builds a flavor combination that's nearly irresistible.

The biggest rule when cooking with fish sauce is to not overuse it. It's a delicate ingredient because of its strong flavor — similarly to how you might add just a dash of Worcestershire or horseradish to a recipe. For every 2 quarts of beef stock you add to the soup, you only need about 1 teaspoon of fish sauce.

Fish sauce is widely available in most grocery stores; it's usually found in the same aisle as other Asian sauces and ingredients. It's typically sold in bottles, but you won't need to use anywhere near a whole bottle for this recipe. However, there is good news: it can last between two to three years once it's opened, especially if it's stored in the refrigerator (you don't have to refrigerate it, but it helps maintain its quality). And you aren't just limited to using it in French onion soup. You can use fish sauce in countless other ways, including in sauces and dressings — plus, it pairs well with other seafood dishes and even steak.