Citizens, this is an almost lost version of onion soup, rarely seen today outside of France and most specifically the city of Lyon, from where this rich and delicious recipe originates!
Be sure and DO use the egg yolk and port – it is what makes this classically Lyonnais! And as for using water instead of good beef stock – the horror!
As noted by Jacques Pepin:
From the Lyon region of France, this onion soup is much thicker than the usual kind. It’s often served as a late-night dish. When I was a young man, I often made it with my friends at two or three A.M. after returning home from a night of dancing.
The soup is strained through a food mill and put in a large tureen or casserole that goes into the oven. Once it is baked, egg yolk and port are mixed together in front of your guests and poured into a hole made in the center of the cheese crust.
Then the whole soup is mixed together — both the crust and the softer insides — and served in hot bowls. It looks thick and messy, but it is delicious!
Citizens, you simply MUST try my recipe!
¾ pound yellow onions, sliced as thinly as possible
5 tablespoons unsalted butter
¼ cup flour
Freshly ground pepper
6 cups beef stock
3 sprigs fresh thyme, tied into a bundle with kitchen string
½ loaf French-style crusty bread or 4 slices firm white bread
¾ pound Gruyère cheese or other Swiss-style cheese such as Emmenthaler
⅓ cup cognac
1 egg yolk
¾ cup port wine
Finely chopped parsley, garnish
Preheat the oven to 400 degrees.
Arrange the bread slices on a cookie sheet and bake for 8 to 10 minutes, until browned. Remove from the oven and set aside. (Leave the oven on.) Melt the butter in a large saucepan. Add the onions and sauté for 15 minutes, or until dark brown.
Add the stock, cognac, thyme, salt, and pepper. Bring to a boil and cook for 20 minutes. Push the soup through a food mill.
Arrange one third of the toasted bread in the bottom of an ovenproof soup tureen or large casserole. Sprinkle with some of the cheese, then add the remaining bread and more cheese, saving enough to sprinkle over the top of the soup.
Fill the tureen with the hot soup, sprinkle the reserved cheese on top, and place on a cookie sheet. Bake for approximately 35 minutes, or until a golden crust forms on top.
At serving time, bring the soup to the table. Combine the yolk with the port in a deep soup plate and whip with a fork.
With a ladle, make a hole in the top of the gratinée, pour in the wine mixture, and fold into the soup with the ladle. Stir everything together, garnish with chopped parsley and serve.