French Onion Soup

Dinner

Rich, golden broth brimming with caramelised onions, crowned with bubbling cheese and crisp baguette. Whether you’re chasing away a chill, or a hangover, this dish does the job deliciously every time.

Pin recipe Print

Prep Time 20 minutes mins

Cook Time 50 minutes mins

Total Time 1 hour hr 10 minutes mins

Servings 4

Ingredients 

1x2x3x?

• 750 gr onion
• 75 gr unsalted butter
• 2 l vegetable stock
• 125 ml dry white wine for example a Waitrose Blueprint White Burgundy
• 1 baguette
• 200 gr Comté cheese or Gruyère or Emmental
• 1 thyme optional, for aroma
• 1 bay leaf optional, for aroma
• salt and black pepper

Equipment

1 dutch oven

1 wooden spoon

1 knife

1 chopping board

1 grater

4 ovenproof soup bowls

1 baking tray

Instructions

1. Prepare and caramelise the onions

• Peel and finely slice the onions. In a large saucepan over a gentle heat, melt the butter. Add the onions and a generous pinch of salt. Cook slowly, stirring often, until the onions are soft, golden, and deeply caramelised, this can take 30 to 40 minutes. Don’t rush this step is the soul of the soup.

2. Build the base

• Pour in the white wine to deglaze the onions, and allow it to bubble away, scraping up any sticky bits from the bottom of the pan. Add the stock, thyme, bay leaf, and a pinch of nutmeg. Bring to a gentle simmer, cover, and cook for 20 minutes so the flavours meld together. Season with salt and pepper to taste.

3. Prepare the bread

• While the soup simmers, preheat your grill (or oven at 200°C). Slice the baguette into thick rounds and toast them on a baking tray until golden. Generously top each slice with grated cheese and return to the grill until the cheese is bubbling and golden.

4. Finish and serve

• Remove the thyme and bay leaf from the soup. Ladle the hot soup into ovenproof bowls. Float a few cheesy croutons on top of each bowl, and if you’re feeling indulgent, scatter over a bit more cheese and pop the bowls under the grill for a few minutes until the top is gloriously gratinéed. Serve immediately, piping hot and bubbling.

Notes

• Really take your time caramelising the onions. The deeper the colour, the richer and sweeter your soup will taste. If you rush this bit, you’ll miss out on that classic, almost jammy depth that makes French onion soup so special.
• If you’re feeling a little rebellious, try a mix of Gruyère and Comté for the croutons. The blend gives you that perfect balance of melt and tang.
• Day-old baguette works best for the cheesy croutons. It holds up beautifully in the soup and soaks up all that savoury broth without falling apart.
• If you’re making this ahead, the soup itself keeps brilliantly in the fridge for up to three days. Just add the cheesy croutons fresh when you’re ready to serve.

About this recipe

French onion soup is one of those dishes that has been feeding people for a very long time, and for good reason. Caramelised onions, rich beef broth, a thick slice of bread, and melted cheese bubbling on top. Simple ingredients, proper technique, and a result that tastes like someone spent the whole day in the kitchen. They didn’t, but the soup doesn’t give that away.

Where french onion soup comes from

Onion soup has roots stretching back to Roman times, when onions were cheap, abundant, and one of the few vegetables available to ordinary people year-round. For centuries it was known as the soup of the poor, a practical meal made from what was always to hand. Onions, bread, and whatever liquid was available. The cheese came later, once the dish made its way into kitchens with access to better ingredients.

The version most people recognise today became a Parisian classic in the markets of Les Halles, the great central market that fed Paris from the 12th century until its demolition in the 1970s. Workers at the market started their shifts before dawn and needed something hot, filling, and fast. French onion soup was all three. It became so associated with Les Halles that it was known as soupe des Halles, and the tradition of eating it in the early hours after a long night became part of Parisian culture.

The legends attached to this french onion soup dish are numerous and probably embellished. Louis XV supposedly made a version with onions, butter, and champagne after a late-night hunt when he found himself hungry with nothing else available. The Duke of Lorraine is said to have demanded the recipe on the spot after trying it at a Champagne inn. Whether either story is true matters less than the fact that a soup this good accumulates stories naturally.

Why making french onion soup takes time

The soup itself is simple. The patience required is not. The entire flavour of a proper french onion soup dish comes from the caramelisation of the onions, and that process cannot be rushed. Onions cooked quickly turn soft and slightly bitter. Onions cooked slowly over low heat for forty minutes to an hour turn sweet, deeply golden, and complex in a way that transforms the entire broth.

This is the step where most onion soup goes wrong. The temptation to turn up the heat when the onions are taking too long is understandable and almost always a mistake. Low heat, patience, and occasional stirring. The colour should develop gradually from white to pale gold to deep amber over the course of the cooking. When the onions look almost too dark, they’re ready.

The broth matters too. A good stock, properly seasoned, gives the soup the body and depth that a weak or oversalted stock can’t provide. If you’re using bought stock, taste it before it goes in and adjust the seasoning accordingly.

The gratin on top

The cheese and bread topping is what makes this a french onion soup dish rather than just onion soup. A thick slice of good bread, slightly stale so it doesn’t dissolve immediately, goes on top of the soup in the bowl. Grated Gruyère or Comté goes over the bread and the soup, and the whole thing goes under a hot grill until the cheese melts, bubbles, and starts to colour at the edges.

The bread absorbs the broth from below whilst the cheese browns from above. By the time it reaches the table, the bread has softened into the soup and the cheese has formed a crust that you have to break through to reach the liquid underneath. That moment of breaking the cheese crust is the best part of eating this soup.

The right pot for french and onion soup

Making french onion soup properly requires a pot that distributes heat evenly for the long, slow caramelisation stage and then holds that heat steadily once the broth is added. Cast iron is ideal for both. I use the Staub cast iron cocotte for this recipe. The heavy base means the onions caramelise evenly without hot spots that catch and burn. The lid traps moisture during the early cooking stage, then comes off for the final caramelisation. And the enamel interior doesn’t react with the acidity of the wine that goes into the broth. It goes straight from hob to table for serving, which for a soup this good is exactly the right approach.

French onion soup after midnight

In some parts of France, particularly at weddings, french onion soup is still served after midnight as the evening winds down. The tradition comes from the Les Halles market culture, where the soup was the thing you ate when the night had gone on too long and you needed something restorative before going home. Whether it works as well at a wedding table as it did in a market café at 4am is debatable. The soup is still worth making either way.