Most French onion soup recipes are made with beef broth, and kosher recipes tend to substitute artificial beef boullion. This one has loads of natural flavor and is made with organic vegetable broth. Be sure you're prepared to have LOTS of patience to bring out the caramelized flavor of the onions. This is not a quick soup to make, but your efforts will be rewarded :)
3 lb yellow onions, cut into ⅛-inch slices
3 Tbsp unsalted butter
1 pinch sugar
8 cup organic vegetable stock (e.g. Imagine or Pacific)
½ tsp salt, plus more as needed
1 Tbsp flour
1 sprig fresh thyme
Melt butter in large pot over medium heat. Add onions, 1/2 teaspoon salt, and sugar. Stir. Cover and cook for 10 minutes.
Take the cover off, and cook, stirring frequently, until the onions are lightly and evenly browned. This may take up to 90 minutes.
Now stir every 5 minutes and add water (1 Tbsp at a time, to loosen up the brown stuff sticking to the bottom of the pan).
Continue to cook until the onions are dark brown in color, approximately 30 minutes.
Add the flour and stir constantly for two minutes.
Add the broth and the fresh thyme to the onions and bring to a boil. Simmer on low heat 20 minutes.
Add salt to taste.
This is delicious served as-is, but it's even better if you ladle it into oven-proof bowls, lay a piece of crusty bread on top of each, and top with loads of Swiss cheese. Pop it under the broiler for just a minute or two to melt the cheese.