The key to a good onion soup is time and patience. The onions must cook for a long while. As they cook, they will sweat, break down and release their juices. The juices must then be allowed to caramelize and form a crust which is deglazed with a fortified liquid. This is what will give the soup its rich brown color and deeply flavorful stock. If you skip this process, you will miss in the soup an extra depth of flavor and body that will leave you struggling to improvise as you desperately rummage through your spice cabinet for that extra something that is missing. There is no substitution for time to achieve this result.
The good news is that there is little effort involved for the cook, except for the exertion of patience. Once the onions are sliced, they are popped in the oven for 3 hours, requiring a mere stir from time to time. During this time you are free to get on with the hustle and bustle of your holiday preparations, secure in the knowledge that at the end of the day you and your family will be rewarded with a rich, warming and nutritious soup. A little comfort and care goes a long way at this time of year. Happy Holidays!
French Onion Soup au Gratin
4 tablespoons unsalted butter
5 large yellow onions, about 3 pounds, halved and thinly sliced
1 teaspoon salt
1/2 cup dry white wine, divided
1/2 cup sherry or Calvados brandy
5 cups beef stock or a combination of beef and chicken stock
4 thyme sprigs, tied with kitchen string
1 bay leaf
Salt and freshly ground black pepper
12-15 baguette slices, cut 3/4 inch thick
1 cup grated alpine cheese such as Grùyere, Comté or Emmenthaler
Preheat oven to 400 F. (200 C.) Melt butter over medium heat in a large Dutch oven or heavy oven-proof pot with lid. Add onions and salt. Cook, stirring, 5 minutes. Cover pot and place in oven for one hour.
Remove pot, stir onions and any collected brown bits on sides and bottom of pot. Cover, leaving slightly ajar and return pot to oven. Cook until onions are soft and golden brown, two hours, checking and stirring up browned bits after one hour. (There will be a lot of liquid in the pot at this point.)
Remove pot from oven and remove lid. Transfer to stovetop. Simmer over medium heat until liquid evaporates and onions turn brown, stirring and scraping up any browned bits on bottom and sides of pot, about 20 minutes. Continue cooking to allow a crust to form on the bottom of the pan without burning, about 5 minutes. Add 1/4 cup white wine to deglaze pan and loosen crust. Continue cooking until wine evaporates and another crust begins to form. Deglaze a second time with remaining 1/4 cup wine. The onions should be dark brown at this point. Add sherry, and cook stirring until sherry evaporates. Add stock, thyme and bay leaf. Stir and scrape up any brown bits on bottom and sides of pot. Bring to a boil, reduce heat and simmer, covered, 30 minutes. Discard thyme and bay leaf. Season with salt and pepper to taste.
Make the croutons:
While the soup simmers, lightly brush bread slices with olive oil. Place on a baking sheet and bake in 400 F. (200 C.) oven until light golden and crisp, 5-8 minutes. Remove and set aside.
Finish the soup:
Divide soup evenly among 4 oven-proof bowls or crocks arranged on a baking sheet. Gently lay croutons in one layer to cover most of the surface. Sprinkle cheese evenly over crouton and soup. Place baking sheet in oven under grill element. Broil until cheese is bubbling and golden brown, 2-3 minutes. Remove from oven and serve immediately.
If you like this, you might enjoy these warming soup recipes:
Farro, Kale and Butternut Squash Soup from TasteFood
Roasted Apple and Winter Squash Soup from the Kitchn
Salmon Chowder with Cauliflower and Spinach from TasteFood
Lentil and Sausage Soup from Food52
Potato Leek Soup from Pinch My Salt