When I first got Julia Child’s Mastering the Art of French Cooking I went on a recipe testing frenzy. I tried every variation of this soup with stocks and wines. We came to the conclusion that a combination of red and white wine with dark chicken stock was the best all around version.

5-6 Cups Yellow Onions, sliced thin
1/2 Yellow Onion, raw
1/4 cup/60ml Olive Oil
French Bread, about 8 slices
2-3 tablespoons/30-45ml cognac
4 ounces/113g Grated Parmesan Cheese
12 ounces/340g Swiss Cheese, Grated
Salt and Pepper
1/2 teaspoon/2ml Ground Sage
1 Bay Leaf
1 cup/250ml Dry White Wine (we prefer 1/2 dry white 1/2 dry red/burgundy)

6 cups/1.4 liters Beef Stock or chicken stock (we prefer dark chicken stock)

3 tablespoons/45ml/45 g Flour
1/2 teaspoon/2ml Sugar
2 tablespoons/29gButter

1 tablespoon/15ml Cooking Oil

Heat a heavy, oven-safe, stock pot over medium-low heat and add cooking oil once the pot is hot. Melt the butter into the hot oil.  Stir the sliced onions into the oil/butter mix, ensuring they are evenly coated. Cover the stock pot and cook for around 20 minutes checking to make sure they aren’t burning. Onions should be clear and very tender once finished. Turn up the heat to medium-high, and add the sugar and 1tsp salt. Continue cooking while stirring until onions are thoroughly browned (caramelized).

Reduce heat to medium-low and stir in flour. Cook 2-3 minutes until flour forms a thick paste (add more butter if needed).  Stir in 1 cup/250ml of stock, and stir heavily for a couple seconds.
Add the rest of the stock, wine, sage, and bay leaf. Bring to a boil, then reduce heat and simmer for 30 minutes.

Pre-heat oven to 325F/165C/Gas 3

Drizzle both sides of french bread slices with olive oil, and place on a baking sheet. Cook the bread in the oven for 15 minutes on each side.

Taste soup, and add salt and pepper as needed, then remove the bay leaf.

Add cognac, and grate the 1/2 raw onion into the soup. Add a little bit of the swiss cheese to the soup, preserving most of it for the top. Cover the soup mixture with the bread, forming a single layer bread top. Sprinkle the rest of the Swiss cheese over the top of the bread, forming a thick layer. Drizzle melted butter or oil over the cheese, and place the pot into the oven uncovered. Bake for around 30 minutes, or until cheese is melted. Turn the broiler on and brown the cheese.

Remove pot from the oven and let stand to cool.