Slow-Cooked French Onion Soup with Melted Gruyère Topping

Kitchen Team @ Spooning and Forking

French onion soup is all about patience: onions caramelised until golden, simmered into broth, and topped with bubbling Gruyère on toasted bread. A warming, comforting dish perfect for slow evenings and impressive enough for entertaining during the colder months.

No ratings yet

Print Recipe Pin Recipe

Prep Time 15

Cook Time 2

Course Soup, Starter

Cuisine European, French

Servings Servings

Calories 420 kcal

Ingredients

1.2 kg Onions (a mix of yellow and red works well), thinly sliced
60 g Butter unsalted
2 tbsp Olive oil extra virgin
2 tsp Sea salt
1 tsp Sugar
3 cloves Garlic minced
2 tbsp Flour plain
250 ml White wine dry
1.5 l Beef stock or vegetable stock for vegetarian
3 sprigs Thyme
2 Bay Leaves
1 Baguette sliced into rounds
200 g Gruyère cheese, grated
Black pepper to taste, freshly ground

Instructions

Set a heavy-bottomed pot over medium-low heat. Add butter and olive oil, then tumble in the sliced onions with salt and sugar. Cook gently, stirring often, for 40–50 minutes until the onions are deeply caramelised, golden brown, and sweet. Don’t rush this stage—it’s what gives the soup its depth.
Stir in the garlic and flour, cooking for two minutes to eliminate any rawness. Deglaze with white wine, scraping the bottom of the pot to release caramelised bits. Pour in the stock, tuck in thyme and bay leaves, and bring to a simmer. Cook uncovered for 30 minutes, stirring occasionally. Remove the herbs, season with pepper, and ladle into ovenproof bowls.
Place baguette slices on top of each bowl, cover with Gruyère, and place under a hot grill until the cheese is molten and bubbling. Serve straight away, though mind your tongue—the cheese top will be lava-like at first bite.

Notes

Onions are, naturally, the heart of this recipe. A mix of red and yellow gives both depth and brightness, but if you’ve only got one type, it will still work beautifully. It’s worth slicing them evenly so they caramelise at the same pace, avoiding burnt stragglers.

Gruyère is the classic choice, its nutty sharpness melting into luscious strands. If you can’t find it, Comté or Emmental make good stand-ins. Vegetarian versions of Gruyère-style cheeses are increasingly easy to find, making it possible to enjoy this soup without compromise.

Nutrition

Calories: 420kcalCarbohydrates: 38gProtein: 16gFat: 22gSaturated Fat: 12gPolyunsaturated Fat: 2gMonounsaturated Fat: 6gCholesterol: 55mgSodium: 980mgPotassium: 610mgFiber: 4gSugar: 12gVitamin A: 880IUCalcium: 280mgIron: 2.5mg

Keyword caramelised onions, comforting soup, French onion, melted Gruyère, winter recipe

Tried this recipe?Let us know how it was!