Six large or nine small onions (peeled and thinly sliced), 40ml of port, 40ml of balsamic vinegar, two litres of chicken stock, 12 slices of baguette loaf, 125g of butter, 250g of Gruyere cheese, one bouquet garni, salt and pepper, 85g of cubed pancetta
Melt the butter over medium heat until it starts to go brown, but only just. Add the onions, and cook them over medium heat, stirring occasionally, until they are soft and evenly browned. Turn up the heat and stir in the port and vinegar, scraping the residue off the bottom of the pan to release the flavours. Add the chicken stock, the pancetta and bouquet garni and bring it to the boil. Now turn down the heat and leave the pot to simmer for 45 minutes to an hour. Using a large flat spoon, remove any foam or scum that bubbles to the surface. Lift out the bouquet garni when the soup is ready, and add a touch of salt and pepper.
Brush the baguette slices with olive oil, and toast them on either side under a hot grill. Grate the cheese. Put the soup into oven-proof soup bowls. Place two slices of toasted bread on the surface, sprinkle on the grated cheese, then put the soup-bowls into the oven at180C, until the cheese melts and it starts to crisp up and brown. A few burnt bubbles are acceptable – they even add to the flavour – but don’t allow the cheese to burn.
If you don’t have oven-proof soup-bowls, put the toasted bread at the bottom of the bowls and top it with cheese, and then put the bowls into the oven briefly until the cheese melts. Ladle the soup onto the bread and cheese.
