Credit to Julia Childs. With mushrooms added.
- 1.5 lbs onions, sliced
- 0.5 lbs button mushrooms, cleaned and cubed
- 3 Tbs butter
- 2 Tbs olive or other cooking oil (divided)
- 1 tsp salt
- 0.25 tsp sugar
- 3 Tbs flour
- 2 quarts beef broth (can sub veggie broth to make it vegetarian)
- 0.5 cups dry white wine
- 3 Tbs cognac
- French bread
- 2 cups grated Gruyere cheese
You will need oven-safe bowls or ramekins to bake cheese on at the end.
Place 1 Tbs oil and butter in large soup pot (dutch oven works great). Heat on medium until the butter is melted.
Add the onions, lower the heat, cover, and cook slowly for 15 minutes.
Remove the cover, add the salt and sugar, and cook slowly for 30-60 more min until the onions are caramelized & browned. The should take on a deep brown color. Stir often, and if needed to prevent burning you can add 1 Tbs water.
When browned to your liking, sprinkle flour over the onions, stir to coat, and cook off the flour taste for roughly 2 minutes.
Separately, heat beef broth to boiling.
Add the mushrooms and remaining 1 Tbs oil to the pot with the onions, stir and cook until the mushrooms have released their liquid and browned slightly.
Add the boiling beef broth to the onions, and stir to loosen the fond from the bottom of the pot. Add the white wine, and let the soup simmer for about another 30 minutes.
Stir in the cognac. The soup is done now; you can eat it immediately, or preferably refrigerate overnight to improve the texture and flavor.
When ready to eat, preheat the oven to 325°, toast inch thick slices of French bread, heat soup to boiling. Ladle the soup into an oven safe bowl, and top with the French bread and handfuls of the Gruyere cheese, and possibly a drizzle of olive oil. Place in the oven for 20 minutes, then broil for a few minutes to brown the cheese on the top.