1Peel the onions and slice them very thinly into half-moons.
2Melt the butter in a large heavy-bottomed pot over medium-low heat. Add the onions and a pinch of salt. Cook slowly, stirring regularly, until very soft and deeply golden brown.
3Sprinkle the flour over the onions, stir well and cook for 1–2 minutes.
4Pour in the white wine, scraping up all the caramelized bits from the bottom of the pot. Let it simmer for 2–3 minutes.
5Gradually add the beef stock, thyme and bay leaves. Bring to a gentle simmer and cook uncovered for 25 minutes. Season with salt and freshly ground black pepper. Remove the thyme stems and bay leaves.
6Slice the baguette and toast at 180°C / 350°F until golden and crisp.
7Ladle the soup into oven-safe bowls. Sprinkle a little grated cheese over the soup, place one toasted baguette slice on top, then generously cover with grated Gruyère cheese.
8Place the bowls under the grill at 220–250°C / 425–480°F, until the cheese is melted, bubbling and golden.
9Finish with a little fresh parsley. Let the soup cool slightly before serving.
Ingredients
750 g yellow onion
2 tbsp unsalted butter
1.5 tbsp all-purpose flour
150 ml dry white wine
1 l beef stock
2 sprigs fresh thyme
2 piece bay leaf
salt (optional)
freshly ground black pepper (optional)
1 piece baguette
150-200 g gruyère cheese
fresh parsley (optional)
Equipment
large heavy-bottomed potknifecutting boardspatulaovengrateroven-safe bowls
Tips
Take your time with caramelizing the onions, as it's the key to the soup's deep flavour.
The soup will be very hot straight out of the oven, so let it cool slightly before serving.