5tbs olive oil
4 medium yellow onions, peeled, halved through the stem end, and sliced 5mm thick
15g unsalted butter
1 garlic clove, peeled and thinly sliced
4 sprigs of thyme
1 bay leaf
1⁄4tsp freshly ground white pepper
185ml dry white wine
2 litres chicken stock (good-quality stock cubes will do)
6 slices of country bread, about 2.5cm thick, toasted
200g Gruyère cheese, coarsely grated
METHOD Heat the olive oil in a large, heavy-based saucepan over a medium flame. Add the onions and, stirring frequently to prevent burning, sauté until they reach a golden colour; this will take approximately 30 minutes.
Add the butter, garlic, thyme, bay leaf, salt and pepper and cook for 10 minutes. Raise the heat to high, add the white wine and boil until it has reduced by half, about 3 to 5 minutes. Add the chicken stock and simmer for 45 minutes.
Preheat the grill.
Remove the thyme sprigs and bay leaf, and swirl the port into the finished soup. Ladle the soup into 6 ovenproof bowls. Fit the toasted bread into the bowls on top of the liquid and sprinkle the Gruyère onto each slice. Place under the grill for 3 minutes, or until the cheese melts to a crisp golden brown. Allow the soup to cool slightly, about 3 minutes, before serving.