Vegetarian French Onion Soup

Ingredients

• 28 g (2 tablespoons)butter (or olive oil)
• 8yellow onions, thinly sliced
• 1 teaspoon, plus more to tastesea salt
• 3bay leaves
• 120 ml (½ cup)dry white wine
• 2sprigs of rosemary, leaves removed and optionally roughly chopped (about 5 cm long each)
• 1.2 litres (5 cups)hot water
• ½ French loaf, cubed (about 480 ml, or 2 cups)French bread
• 57 g (2 ounces), or more or less as desiredGruyère or mature white Cheddar, freshly grated
• To taste, optionalgreen onion, diced, for garnish

Instructions

1. 1

   Soften the onions

   Melt the butter in a large, heavy-based pot over medium heat. Add the onions, salt and bay leaves, cover and cook over medium-high heat for 4–5 minutes, until the onions begin to turn translucent and release liquid.

2. 2

   Caramelise slowly

   Remove the lid and cook the onions over low to medium-low heat until deeply caramelised. This takes 2–5 hours, depending on the pot size and heat. Check about once an hour, except more often at the beginning and end. The onions can be cooked ahead and frozen until needed.

3. 3

   Add the wine

   Once the onions have reduced and turned amber, raise the heat to medium-high and pour in the wine. Let it boil down for 3–4 minutes.

4. 4

   Simmer the soup

   Add 1.2 litres of hot water and the rosemary, then bring to the boil. Reduce the heat and simmer. Taste the soup; add another 240 ml of hot water for a milder flavour, another splash of wine if you like, or extra salt if it tastes bland. Remove the bay leaves.

5. 5

   Heat the grill

   Turn on the oven grill.

6. 6

   Grill in bowls

   If your bowls are oven-safe, ladle in the soup and place bread on top. Add as much cheese as you like, set the bowls on a baking tray and grill for 1–2 minutes, until the cheese is melted and golden. Garnish with fresh herbs if desired and serve immediately.

7. 7

   Grill bread separately

   If your bowls are not oven-safe, put the bread cubes on a baking tray and top with cheese. Grill for 1–2 minutes, until the cheese is melted and golden. Ladle the soup into bowls, add the cheese-topped bread and garnish with fresh herbs if desired. Serve immediately.

What is vegetarian French onion soup?

French onion soup is known for its slowly cooked onions and bread-and-cheese topping. This vegetarian version builds its broth from the onions themselves, using water, wine and rosemary instead of beef broth.

The key is giving the onions time to reduce and turn amber. Their concentrated sweetness makes a simple, onion-led soup that pairs well with the rich, browned topping.

Nutrition and macros by portion

The nutrition label shows one serving as written: 221 calories, 6g protein, 21g carbs, 10g fat.

The onions and bread provide most of the carbohydrates, while butter or oil and cheese contribute much of the fat; the cheese also supplies some protein. For a more balanced plate, serve a bowl with a generous green salad or other vegetables.

Give the onions time

Even slicing: Cut the onions into similarly thin slices so they soften at a similar rate. A heavy-based pot helps distribute the heat during the long cook.

Slow cooking: Keep the heat low or medium-low after the initial covered stage. The onions should gradually shrink and deepen in colour rather than scorch.

Build the broth

Dry wine: Let the wine boil down for 3–4 minutes after adding it to the caramelised onions. This keeps its acidity and aroma in balance with their sweetness.

Rosemary and water: Add hot water and rosemary, then simmer the soup. Taste before adjusting: extra water gives a gentler flavour, while salt can lift a broth that seems flat.

Watch for the right colour

Amber onions: They should be greatly reduced and a deep amber shade before you add the wine. The recipe allows 2–5 hours, so use the colour and reduced volume as cues rather than relying on the clock alone.

Golden cheese: Grill the bread until the cheese has melted and turned golden, about 1–2 minutes. Keep an eye on it, as the topping can brown quickly.

Choose how to finish it

Oven-safe bowls: Put the bread and cheese directly on the soup, then grill the filled bowls on a baking tray. Make sure the bowls are suitable for the oven before using this method.

Separate topping: If your bowls cannot go under the grill, brown the bread and cheese on a baking tray and set it on the soup just before serving.

Serve it straight away

The bread topping is best while the cheese is hot and the bread still has some structure. Add the optional diced green onion or fresh herbs just before serving.

A simple green salad makes a fresh accompaniment. Serve the soup as a starter or pair it with a salad and extra bread for a more substantial meal.

Recipe notes & tips

• Slice the onions evenly to help them cook at the same pace.
• Use a heavy-based pot to make the long, slow cooking easier to manage.
• Check the onions more frequently as they begin to colour and near the end of caramelising.
• Taste the broth after simmering before adding more salt, water or wine.
• Prepare the caramelised onions in advance and freeze them if convenient.
• Grill the cheese topping just before serving for the best texture.

Variations

• Use olive oil: Swap it for the butter to make the soup dairy-free before adding the cheese.
• Change the cheese: Use mature white Cheddar instead of Gruyère, as suggested in the recipe.
• Adjust the broth: Add up to 240 ml more hot water for a milder onion flavour.
• Add more wine: Stir in another splash if you want a more pronounced wine note.
• Skip the garnish: Leave off the optional green onion or use fresh herbs if desired.

Common mistakes to avoid

• Cooking too hot: The onions can scorch before they caramelise; keep the heat low or medium-low.
• Stopping too early: Pale onions have not reached the recipe's amber stage; continue cooking until reduced and deeply coloured.
• Adding wine before caramelising: Wait until the onions are amber so they can develop their flavour first.
• Over-grilling the topping: Cheese can brown quickly; watch it closely during the 1–2 minutes under the grill.
• Using unsuitable bowls: Non-oven-safe bowls should not go under the grill; brown the bread and cheese separately instead.

How to store

The recipe suggests cooking the caramelised onions ahead and freezing them until needed. The finished soup is best served immediately after adding the grilled bread and cheese; store any leftover soup separately from the topping in a covered container in the fridge and reheat the soup gently on the hob.

Frequently asked questions