French Onion Soup

There’s something undeniably comforting about French onion soup. The rich, savoury broth infused with slow-cooked onions, the crisp baguette soaking up all that goodness, and the golden, bubbling gruyère create a dish that’s both rustic and elegant. It’s a true testament to how simple ingredients can transform into something spectacular when treated with care.

This soup has been a staple in French cuisine for centuries, yet it remains just as beloved today as it was in the past. Whether served as a starter or a main course, it never fails to satisfy. 

Table of Contents:

• Ingredient Breakdown
• The History Behind French Onion Soup
• The Secret to Perfectly Caramelised Onions
• Building Flavour: The Role of Stock and Sherry
• Choosing the Right Cheese for the Perfect Melt
• Crafting the Perfect Cheese Toast
• Bringing It All Together
• How to Store and Reheat French Onion Soup
• Welcome To Soup Season!

Ingredient Breakdown

• Unsalted butter: Adds richness and depth to the caramelised onions, creating a smooth and luxurious base for the soup.
• Extra-virgin olive oil: Enhances the butter’s flavour while preventing it from burning, ensuring the onions cook evenly.
• White onions: The star of the show, providing a natural sweetness that defines the dish. Their slow transformation is key to developing the signature depth of flavour.
• Garlic: A subtle but essential aromatic that enhances the depth of flavour.
• Beef stock: The backbone of the soup – using a high-quality stock makes all the difference. A rich, well-made beef stock contributes a robust umami taste that elevates the soup to another level.
• Dry sherry: Lends complexity and enhances the umami depth, balancing the overall flavour.
• Thyme: A fragrant herb that complements the onions beautifully adding an earthy undertone.
• Bay leaf: Infuses a subtle earthiness into the broth, enhancing its complexity.
• Baguette: The perfect crunchy contrast to the velvety soup.
• Gruyère: A nutty, melt-in-the-mouth cheese that forms the irresistible topping.
• Fresh chives: A finishing touch that brightens the dish.

The History Behind French Onion Soup

French onion soup has a fascinating history, dating back to the 18th century. Originally considered a humble dish enjoyed by labourers, it gradually gained popularity across France. The combination of caramelised onions and broth has been a staple in French cuisine for centuries, but it was the addition of toasted bread and melted cheese that elevated it into a culinary icon. Today, it’s served in restaurants worldwide, proving that simple, well-prepared ingredients never go out of style.

The Secret to Perfectly Caramelised Onions

Patience is key when it comes to caramelising onions for French onion soup. Rushing this step results in bitterness rather than the deep, mellow sweetness that defines the dish. Cook the onions low and slow in butter and olive oil, stirring occasionally to ensure they soften evenly. As they release their natural sugars, they’ll turn golden brown and develop an incredible depth of flavour. The process takes at least 45 minutes but is entirely worth the effort. A pinch of salt early on helps draw out moisture, speeding things up slightly.

If you find the onions sticking to the pan, a splash of water or stock can loosen them while preventing burning. The key is patience – allowing the onions to cook slowly ensures they reach their full potential, delivering a deep, almost jam-like consistency that forms the foundation of the soup.

Building Flavour: The Role of Stock and Sherry

Once the onions reach that perfect caramelisation, it’s time to build layers of flavour. Adding dry sherry deglazes the pan, lifting all the rich, sticky bits from the bottom and intensifying the soup’s depth. Let it reduce before pouring in the beef stock, which should be of the highest quality you can find. A homemade stock is ideal, but a well-sourced, rich store-bought version works just as well. The broth simmers with thyme and bay leaf, allowing the flavours to meld beautifully over time.

The result is a deeply savoury, complex soup that embodies the essence of slow cooking. As the soup simmers, it continues to develop richness, with each ingredient contributing its unique flavour, leading to a well-rounded dish that is rich, yet balanced.

Choosing the Right Cheese for the Perfect Melt

Gruyère is the traditional choice for French onion soup, thanks to its nutty flavour and excellent melting qualities. However, if you want to experiment, Comté, Emmental, or even a well-aged cheddar can work beautifully. The key is selecting a cheese that melts smoothly while offering a rich depth of flavour. For an extra indulgent touch, a mix of cheeses can create an even more complex and satisfying topping.

Cheese selection is crucial because it needs to provide both taste and texture. The melted layer should stretch and bubble, creating a contrast with the crisp toast beneath it. A poor cheese choice could result in an oily or overly stringy texture, which would detract from the overall experience.

Crafting the Perfect Cheese Toast

A crucial component of French onion soup is the cheesy, toasted baguette floating atop the bowl. To achieve the ultimate crunch, slice a baguette and toast it until crisp. This step ensures the bread retains its structure when submerged in the soup. Once toasted, generously top each slice with grated gruyère and place it under the grill or bake until melted, golden, and bubbling.

Bringing It All Together

When it’s time to serve, ladle the hot soup into heatproof bowls, place the cheese-laden toast on top, and let the residual heat work its magic. A quick trip to the oven ensures the cheese reaches that irresistible molten state. A sprinkle of finely chopped chives adds a fresh contrast, cutting through the richness.

How to Store and Reheat French Onion Soup

French onion soup is a fantastic make-ahead dish. The flavours deepen overnight, making leftovers just as delicious, if not better! Store the soup in an airtight container in the fridge for up to three days. When ready to serve, reheat gently on the stove, adding a splash of water or stock if it has thickened too much. For the bread and cheese topping, prepare fresh toasts and melt the cheese just before serving to maintain the signature crisp texture.

Welcome To Soup Season!

If like me you love soups, I have so many different recipes for you to choose from. You can access all my soup recipes here. Some of my favourite include:

• Golden Thai Curry Chicken Noodle Soup: This soup is quite literally a hug in a bowl. The star of the show is the umami, flavour-packed broth, which comes together in just 20 minutes.
• Teriyaki Pork Miso Ramen: This ramen is so incredibly flavourful, which is surprising given that the broth comes together in just 5 minutes. The secret weapon is instant dashi, which packs an umami-packed punch that makes the broth taste like it’s been simmering for hours.
• Turmeric Coconut Squash Soup: This autumnal soup is the perfect soup to make on a chilli day. Turmeric and coconut are a match made in heaven and they complement the butternut squash so beautifully.
• Spiced Red Lentil Soup: This thick, creamy vegan spiced red lentil soup is high in protein, packed with flavour and naturally vegan. It’s inspired by the Lebanese classic, shorbet adas.
• Chinese Style Chicken and Sweetcorn Soup: This soup is a comforting classic. It’s perfect for a quick and satisfying meal, especially on cold days when you crave something warm and nourishing.

See how I make these soups and more over on my Instagram!