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French Onion Soup Gratine
5 from 138 votes

French Onion Soup Gratine

French Onion Soup Gratine combines slow-cooked caramelized yellow onions with beef stock, brandy, and white vermouth for a rich broth. This soup is topped with toasted baguette slices rubbed with garlic and melted Gruyere cheese, creating a layered dish of sweet onions, savory broth, and cheesy crust. The long simmering develops deep flavors, while the crouton topping adds a satisfying chew and melt. It’s suited for a hearty starter or a comforting meal in cooler weather.

Prep Time
10 mins
Cook Time
2 hrs 15 mins
Servings: 6 servings
Calories: 436 kcal
Course: Soup
Cuisine: French

Ingredients

  • 3 Tablespoons butter unsalted
  • 1 Tablespoon olive oil
  • 8 cups onion thinly sliced, (about 2 1/2 pounds, yellow
  • 1/2 teaspoon sugar
  • 1/2 teaspoon kosher salt
  • 2 Tablespoons flour
  • 2 1/2 quarts beef stock
  • 4 Tablespoons brandy
  • 1 cup dry white vermouth French
  • 1 prig thyme fresh
  • black pepper fresh, to taste
Cheesy Croutons
  • 1 baguette cut into 3/4" thick slices and toasted, small
  • 1 cup gruyere cheese or Swiss cheese, grated
  • 1 clove garlic
  • 2 Tablespoons olive oil

Instructions

    Cup of Yum
  1. Using a heavy bottomed saucepan, heat the oil and butter over a moderate heat.
  2. Add the onions and cover. Cook over a low heat until tender and translucent, about 10 minutes.
  3. Stir in salt and sugar, raise heat to moderately high and let the onions brown, stirring frequently until they are a golden walnut color, 35 to 40 minutes.
  4. Add flour and cook slowly, stirring, for another 3 to 4 minutes. Remove from heat, let cool a moment, then whisk in 2 cups of hot stock.
  5. When well blended, bring to a simmer, add the rest of the stock, the brandy or Cognac and the vermouth. Add a sprig of fresh thyme.
  6. Cover loosely and simmer very slowly 1 1/2 hours, adding a little more broth if the liquid reduces too much.
  7. Adjust seasoning. At this point taste the broth and decide if it needs any more salt or pepper.
  8. To finish the soup, brush both sides of the bread slices with olive oil, then rub the cut side of a clove of garlic over both sides. Toast under a broiler, flipping until both sides are golden brown.
  9. Ladle soup into oven proof bowls. Preheat broiler.
  10. Float one or two croutons on top of the soup to cover.
  11. Top with grated cheese. Place bowls on a sheet pan.
  12. Place under the broiler, watching carefully, since it will brown fast! Broil until cheese is melted and light golden brown.
Cheesy Croutons
  1. Slice baguette on the diagonal, about 3/4" thick.
  2. Brush each side of the bread slices with olive oil and rub with cut garlic clove.

Notes

  • Caramelize the onions a day in advance for easier assembly on serving day.
  • Use fresh thyme sprigs to infuse the broth with herbal aroma during simmering.
  • Brush bread slices with olive oil and rub with garlic before toasting to add subtle flavor to the croutons.
  • If the broth reduces too much during simmering, add extra stock to maintain consistency.

Nutrition Information

Serving 1serving Calories 436kcal (22%) Carbohydrates 39g (13%) Protein 17g (34%) Fat 19g (29%) Saturated Fat 8g (40%) Polyunsaturated Fat 2g (12%) Monounsaturated Fat 8g (40%) Trans Fat 0.2g (10%) Cholesterol 32mg (11%) Sodium 1275mg (53%) Potassium 1113mg (24%) Fiber 5g (20%) Sugar 13g (26%) Vitamin A 337IU (7%) Vitamin C 16mg (18%) Calcium 288mg (29%) Iron 3mg (17%)

Nutrition Facts

Serving: 6 servings

Amount Per Serving

Calories 436

% Daily Value*

Serving 1serving
Calories 436kcal 22%
Carbohydrates 39g 13%
Protein 17g 34%
Fat 19g 29%
Saturated Fat 8g 40%
Polyunsaturated Fat 2g 12%
Monounsaturated Fat 8g 40%
Trans Fat 0.2g 10%
Cholesterol 32mg 11%
Sodium 1275mg 53%
Potassium 1113mg 24%
Fiber 5g 20%
Sugar 13g 26%
Vitamin A 337IU 7%
Vitamin C 16mg 18%
Calcium 288mg 29%
Iron 3mg 17%

* Percent Daily Values are based on a 2,000 calorie diet.