Ingredients
For the Soup
- 4 large onions (yellow or sweet), thinly sliced
- 2 teaspoons olive oil
- 3 cloves garlic, minced
- 1 teaspoon balsamic vinegar (optional, enhances sweetness)
- 1 tablespoon whole wheat flour or cornstarch (for light thickening)
- 6 cups low-sodium vegetable or beef broth
- 1 teaspoon fresh thyme leaves (or ½ teaspoon dried thyme)
- 1 bay leaf
- Salt and freshly ground black pepper, to taste
- 1 teaspoon Worcestershire sauce (optional, adds depth)
For the Topping
- 2–3 slices whole-grain or sourdough bread, toasted
- 60–80 grams reduced-fat Gruyère or Swiss cheese, grated
- Fresh thyme sprigs for garnish (optional)
Equipment Needed
- Large, heavy-bottomed saucepan or Dutch oven
- Wooden spoon
- Knife and cutting board
- Baking tray
- Oven (for broiling the cheese topping)
- Ladle
Preparation Steps
Step 1: Slice the Onions
Peel and thinly slice the onions. Consistent, thin slices ensure even caramelization and a tender texture.
Step 2: Caramelize the Onions
Heat 2 teaspoons of olive oil in a large saucepan over medium heat.
Add the sliced onions and stir to coat in the oil.
Cook slowly for 25–30 minutes, stirring occasionally. The onions should soften, become golden, and develop a natural sweetness.
Halfway through, sprinkle in 1 teaspoon of balsamic vinegar (optional) to enhance sweetness and color.
Avoid high heat, as this can burn the onions and make the soup bitter.
Step 3: Add Garlic and Flour
Once the onions are deeply golden and soft, add the minced garlic. Stir for 1–2 minutes until fragrant.
Sprinkle the flour over the onions and stir for 1–2 minutes. This helps slightly thicken the soup while keeping it light.
Step 4: Add Broth and Herbs
Gradually pour in the broth while stirring to prevent lumps.
Add the thyme, bay leaf, and Worcestershire sauce if using.
Bring the soup to a gentle simmer. Reduce heat to low and cook uncovered for 15–20 minutes. This allows the flavors to meld.
Season with salt and freshly ground black pepper to taste.
Step 5: Prepare the Bread
While the soup simmers, toast slices of whole-grain or sourdough bread until golden brown.
For added flavor, rub lightly with a cut garlic clove.
Step 6: Assemble for Broiling
Preheat the oven broiler.
Ladle the soup into oven-safe bowls.
Place one toasted bread slice on top of each bowl. Sprinkle the grated cheese generously over the bread.
Place the bowls on a baking tray. Broil for 3–5 minutes, or until the cheese melts, bubbles, and turns lightly golden. Watch carefully to prevent burning.
Step 7: Serve
Remove from the oven using oven mitts.
Garnish with a sprig of thyme if desired.
Serve immediately while hot.
Tips for a Healthier Soup
- Use olive oil sparingly or substitute with a few tablespoons of vegetable broth for cooking onions.
- Use low-sodium broth to reduce salt intake.
- Choose reduced-fat cheese or a moderate portion of full-fat Gruyère.
- Pair with a small portion of whole-grain bread for fiber.
Variations
- Vegan Version: Use vegetable broth and omit cheese or use plant-based cheese.
- Herb Variations: Add rosemary or parsley for extra flavor.
- Mushroom Addition: Sauté 100 grams of mushrooms with the onions for depth.
