French Onion Soup

法式洋蔥湯
Category: Soup
Style: French
Difficulty: Medium
Portion: Serves 8

Ingredients
4 tbsp unsalted butter
2 lb yellow onions
1 tsp sugar
1 tbsp all purpose flour
1/2 cup dry sherry or red wine or brandy
4 cups beef stock
1 tsp dried thyme
salt and pepper to taste
1 french baguette, cut into 1/2 inch slices
8 onces Gruyere, Asiago or Mozzarella cheese, grated on the large holes of a box grater, about 3 cups
1/2 cup freshly grated parmesan cheese

Procedures
Slice onions into 1/4-inch half circles.
Melt butter in a large dutch oven or heavy-pot on medium low heat. Add onions. Spread them out in as thin a layer as possible. Sprinkler with sugar, and cook, stirring as little as possible. Cook until onions are melting and soft, golden brown, and beginning to caramelize, about 30 minutes. You can also place the pot in a 300F oven after the initial sauté-ing for 1 hour to achieve similar result.
Sprinkle flour over onions, and stir to coat. Add sherry, stock and thyme, and bring to a simmer. Cook, partially covered, for about 30 minutes. Season with salt and pepper to taste.
Meanwhile, lightly toast bread under a broiler. Sprinkle cheese over toast, and place under broiler again until cheese is melted and crusty brown around the edges.
To assemble: ladle hot soup into bowl, and place a cheese toast on top of soup. Serve immediately.

Tips
It is easier to make the cheese toast separately, because to melt the cheese directly on the soup like most traditional methods requires broiler-proof soup bowls which most family do not have.
We need to cook the onion as slow as possible so that the flavour will intensify.
You can also mix different kinds of onions (such as red onions and white sweet onions) to create different flavour.
Use low sodium beef stock to avoid overly salty soup.