Here's the original recipe I used. Tonight, I just thawed it out, added some bread and cheese, and threw it under the broiler for a minute. I was freezing after taking the kids to the park (I thought 50 degrees sounded warmer than it actually was) and this soup is so hot, it was perfect!
French Onion Soup (adapted from Smitten Kitchen)
5 cups thinly sliced yellow onions (4 or 5 onions)
3 tablespoons butter
1 tablespoon olive oil
1 teaspoon salt, plus additional to taste
1/2 teaspoon sugar
3 tablespoons all-purpose flour
8 cups beef stock
1/2 cup dry red wine
1 bay leaf
freshly ground black pepper
french bread
swiss cheese, grated
Melt the butter and oil together in the bottom of a Dutch oven over moderately low heat. Add the onions, toss to coat them in oil and cover the pot. Reduce the heat low and let them slowly steep for 15 minutes. They don’t need your attention; now would be a good time to touch up your eye makeup that you cried off during the onion chopping process!
After 15 minutes, uncover the pot, raise the heat slightly and stir in the salt and sugar. Cook onions, stirring frequently, for 45 minutes until they have turned an even, deep golden brown. Don’t skimp on this step, as it will build the complex and intense flavor base that will carry the rest of the soup.
After the onions are fully caramelized, sprinkle them with flour and cook, stirring, for 3 minutes. Add the wine in full, then stock, a little at a time, stirring between additions. Season to taste with salt and pepper. Add bay leaf. Bring to a simmer and simmer partially covered for 30 to 40 more minutes.
****At this point, I instead transferred the soup to a crock pot and cooked it for a few hours on low.
To serve: cut french bread to fit broiler-safe bowls. Broil bread on high for less than a minute, until browned on one side. Put browned side down on top of each soup bowl and top with grated cheese (as much as you want). Put bowls on a cookie sheet and broil soups until bubbly and golden.