The Best Onion Variety For Chef-Approved French Onion Soup

French onion soup can seem like an intimidating dish, but we promise that's just because it has "French" in the name. You don't need to be a master of the country's cuisine or a Michelin-star-awarded chef — you do, however, need lots of patience and the right onions. But, with so many onion varieties at hand, how do you know which is best? We decided to pick an expert's brain on this, speaking to Chef Randy Feltis (@‌KatherineWants on TikTok), the author of Katherine Wants: The Ultimate Date Night Cookbook.

"If you have to go with one onion, the sweet onion is the way to go," he told us. This answer surprised us a bit as, traditionally, what makes French onion soup unique is the use of yellow onions. They're considered a multipurpose variety, with a sharp flavor profile that tends to mellow down as the onions are cooked over a stretch of time. They don't mind simmering for an hour, so it makes sense why they'd be chosen for the classic French soup. 

According to Feltis, however, the sweet onion is the secret top choice because "it offers more sweetness, mellow flavor and caramelizes up nicely." In fairness, those are the exact traits you're essentially expecting from a finished French onion soup. Thanks to their milder nature, another bonus for using sweet onions in the soup is that these types of allium are less likely to make you cry when you're cutting them.

Using only one type of onion in the soup yields a pretty consistent result, and that's definitely the path to choose if you're aiming for a tried-and-tested soup that tastes the same every single time you make it. But, if you're feeling a bit adventurous, a mix of varieties could be the way to go. Chef Feltis' recommendation is to use a combination of three onions, sharing, "I like the different flavours and textures [of] Spanish, sweet and regular yellow onions." 

"You don't want too much sweetness, and you want the boldness from the yellow, so each onion will offer something different to the soup," explains Feltis. This trio also provides balance to the soup. While the sweet — think: Vidalias or Mauis — and Spanish onions are milder options that provide honeyed flavors, the addition of a yellow onion offers a punchier contrasting note for depth. 

That's not where the experimentation has to end, though. You can continue adding ingredients to upgrade your French onion soup. As Feltis suggests, "If you want to get creative, add a shallot." You can also play around with different types of red wine in the broth, or skip the red altogether and add some sherry, instead. But, that's really just the start!