Classic French Onion Soup

The History of French Onion Soup

French onion soup has been around since the 18th century and was originally a simple soup made with onions, bread and cheese. It was called the "poor man's soup" and became a French classic, loved for its rich flavours and comforting warmth.

What’s in French Onion Soup?

For French onion soup you will need a base of thinly yellow onions, beef broth and dry white wine or red wine. Aromatics like garlic, fresh thyme and a bay leaf add depth. To thicken and balance the soup use a little flour, a pinch of sugar and salt and pepper. For the topping, baguette slices and gruyere cheese are musts, but you can also use Comte, Saint Nectaire or even Raclette cheese.

What Cheese To Use for French Onion Soup

Gruyere is the classic choice for French onion soup for its nutty flavour and melting properties. For the best flavour use Gruyère, Emmental de Savoie or Comté. Emmental is nutty and mild, Gruyère is savoury and melts well, while Comté is slightly sweet and complex. Choose one based on your preference or try a mix for a different taste.

For a change of pace you can try Cantal or Saint Nectaire for a mild creamy top. For a heartier finish, Raclette cheese will give you a gooey stretchy texture and bolder flavour. Grate or shred the cheese to evenly cover the baguette slices before broiling until the top is bubbly and golden brown.

How to Caramelize Onions for French Onion Soup?

Caramelizing onions is a slow process that’s the base of traditional French onion soup. Start by cooking the onions over low heat with butter, olive oil and a sprinkle of salt. Stir occasionally until the onions are soft and release their natural sugars. As they turn golden brown you can add a pinch of sugar to help the process along. Deglaze the pan with a splash of wine or balsamic vinegar to scrape up the fond that forms on the bottom. Patience is key—true caramelization takes time but is worth it for that deep sweet flavour.

For the perfect caramelized onions, be sure to cook slowly over low heat to bring out the natural sweetness. Use yellow or sweet onions for best results and stir occasionally to avoid burning. A heavy bottomed pan is best for even cooking.

Add Some Extra Depth to Your French Onion Soup

For a really rich and full flavoured French onion soup add a splash of balsamic vinegar or a dash of Worcestershire sauce during the caramelisation process. These little extras will bring out the sweetness of the onions and the umami from the stock. To make the soup even more intense consider using homemade beef stock or a mix of chicken and vegetable stock for a rounded base. Every spoonful will be satisfying.

Adding Cheese to Your French Onion Soup

You can melt grated cheese over toasted bread but you can also add a layer of cheese into the soup itself. Sprinkle a bit of gruyere in just before serving to create a creamy texture to go with the crispy bread on top.

Variations on the Classic Recipe

Feel free to customize to your liking. For a lighter version use chicken or vegetable stock instead of beef stock and reduce the butter for fewer calories. If you prefer a thicker soup add a teaspoon of flour when caramelizing the onions. If you want to make it a heartier meal add shredded meat from leftover roast beef or chicken for an extra layer of protein. 

Add sautéed mushrooms for an earthy take on this classic recipe or use vegetable broth for a lighter vegetarian version. Try adding thyme or bay leaves to taste.

This recipe is versatile enough to fit any occasion while staying true to the classic.

Can it be made ahead?

Yes French onion soup can be made ahead. Make the soup base and store in the fridge for up to 3 days or freeze for longer storage. To reheat bring the soup to a simmer on the stovetop, then simply assemble and broil with the bread and cheese topping just before serving. This way you can have a batch of soup ready to go even on the busiest of days. For best results thaw frozen soup overnight in the fridge before reheating.

Tips for Storing and Reheating your Onion Soup

French onion soup is a great make ahead or meal prep option. The soup base can be made ahead and stored in the fridge for up to 3 days or frozen in airtight containers for longer storage. To serve, reheat over medium heat, assemble with toasted bread and cheese and place under the broiler until the cheese is golden and bubbly. Perfect for busy nights or dinner parties.

How to Serve French Onion Soup?

French onion soup is best served hot in oven safe bowls. Top the soup with a slice of toasted baguette, then cover with cheese and broil until bubbly. Sprinkle with fresh thyme or black pepper for a fancy touch. Serve with crusty bread or a green salad for a whole meal. Individual servings are perfect for special occasions or family dinner.

For the ultimate fine-dining experience, serve French onion soup in individual oven safe bowls. Place toasted bread on top of the soup, cover with shredded cheese and broil until golden. The result is a bubbly cheesy crust that pairs perfectly with the broth. Add a sprinkle of fresh thyme or black pepper for garnish. Serve with a side salad or crusty baguette for a complete meal.

Why French Onion Soup is a Favourite

French onion soup has been a favourite for centuries because of its simplicity and flavour. Originally a humble dish made from onions and bread it has evolved into a French culinary classic served in the finest restaurants. The combination of caramelized onions, beef stock and grated cheese is a comforting meal that feels indulgent but is surprisingly easy to make. No wonder so many people call it the best soup they’ve ever had.