This Is The Best Type Of Onion To Use In French Onion Soup

From not caramelizing the onions to skipping the classic crouton garnish, there are many mistakes that can spoil a beloved bowl of French onion soup. Make sure you start off on the right track by selecting the best type of onion for the dish.

All onions are not created equal (via Chatelaine). Red onions, for example, shine in raw dishes, thanks to their brilliant hue, and adventurous eaters will appreciate their bold and spicy bite. White onions are another favorite for raw preparations — thanks to a more mild flavor, they're a delicious choice for salads and sandwiches. Ditto for the delicately flavored sweet onion (which you may know by the name of one of the most consumed sweet onion varieties, the Vidalia). 

Looking to get cooking? Say hello to the yellow onion. They're so popular in cooked dishes that they're often referred to as "cooking onions." Peel off their golden skin and you'll unearth a strongly-flavored onion that's perfect for roasts, sauces, sautees, and soups — including the classic French onion.

Julia Child — the chef, author, and TV host credited with America's adoption of French cooking — used yellow onions in her French onion soup (via Julia Child's Recipes). Her version, well-known as a French favorite, calls for 5 to 6 cups of sliced yellow onions slowly caramelized in a combination of butter and cooking oil. The process of caramelization brings out the inherent sweetness in the onions (via Organic Authority). In an onion soup taste-off, Serious Eats noted that yellow onions taste bright and mildly bitter with a sweet finish.

Child's recipe, however, calls for a somewhat controversial ingredient: sugar. The Kitchn reports that the 1/2 teaspoon of sugar spoils the soup — making it overly sweet. They recommend skipping the sugar entirely, noting that while omitting it may add a few minutes to the caramelization process, the final flavor is worth it.

Epicurious agrees that onions add all the natural sugar you need for a sweetly complex soup. However, their recipe calls for sweet onions, not yellow. Cooking solely sweet onions for an hour could result in stock that's a bit too sweet, which can mask the subtle nuances of earthy beef broth, crusty croutons, and salty melted Gruyère. Another option for added sweetness is to cut your yellow onions with slices of sweet (and perhaps even red) onion, for a richly developed and umami French onion soup.