The onion is a rather humble ingredient that usually serves to provide flavor to other dishes. Soupe a l’Oignon, simply known as French onion soup, elevates this culinary workhorse to star status and makes a luxurious meal for two.
Caramelizing onions is definitely a labor of love, however, the result is well worth it. I use a combination of oil and butter to get the process started: Oil keeps the butter from burning and the butter helps caramelize the onions.
Flavor-wise, there is no substitute for the low-and-slow stovetop method. I’ve tried numerous ways to speed the caramelizing process, including doing a large batch in a slow cooker and adding a pinch of sugar. I’ve tried salting the onions right away and not salting the onions until they were done. Both took between 45 minutes to 1 hour to achieve a rich, golden brown color. I now salt the onions after they’ve softened up a bit and focus on their flavor rather than the time to caramelize.
Caramelized onions freeze well, so you may want to double or triple the amount of onions to have them ready for another meal of this soup or for other recipes. When working with a large volume of onions, I place a small fan nearby to blow the tear-producing enzymes away from me. You might also try cutting close to your stovetop exhaust fan or near an open window. Refrigerating onions first will slow the production of those enzymes when the onion is cut.
A good quality beef broth or stock is important for this dish. However, a good chicken broth or mushroom broth may be substituted if you do not care for beef. The splash of white wine at the end is optional. Depending upon the onions used, the result can sometimes be too sweet for my taste. A touch of dry white wine at the end of cooking helps to balance out the flavor.
This luxurious soup is finished with a topping of thick bread slices and melted Gruyere cheese. There are two ways to do this. The first and easiest way is to place the bread slices on a baking sheet, top with the grated cheese, broil for several minutes and serve atop the soup.
The second way is to serve the soup gratinéed, or baked in ovenproof bowls. Toast the bread at 325 degrees for 15 to 20 minutes first, turning once. Place the croutons over the soup, sprinkle with cheese and bake at 350 degrees for 20 to 25 minutes or until the cheese is melted and bubbly, then broil briefly to brown the cheese.
A salad of winter greens such as baby kale on the side rounds out the meal, or serve this as a showstopping first course.
French Onion Soup (Soupe a l’Oignon)
1 tablespoon olive oil
4 tablespoons unsalted butter
2 large yellow onions (about 2 pounds), halved and thinly sliced
½ teaspoon salt
1 bay leaf
2 sprigs fresh thyme
4 cloves garlic, minced
1 tablespoon all-purpose flour
½ cup dry red wine
4 cups low-sodium beef broth or stock
1 to 2 tablespoons dry white wine, if needed
—Black pepper, to taste
1 small sourdough baguette, sliced into 4 thick pieces, ends discarded
¼ pound grated Gruyere cheese
Heat a Dutch oven or other heavy pan over medium-high heat. Add the olive oil and butter; when the butter has melted, add the onions, stirring to coat with the fat. Reduce heat to medium, cover and cook about 10 minutes to soften them and to help bring out some of the moisture, stirring several times.
Add the salt, bay leaf and fresh thyme. Leave uncovered, reduce heat to medium-low and continue cooking, stirring often so the onions brown evenly until the onions are a rich brown color, about 35 to 45 minutes more. Add the garlic and cook 1 minute. Discard bay leaf and thyme sprigs.
Add the wine, bring to a boil and cook until almost evaporated. Stir in the flour and cook 2 to 3 minutes.
Add the beef broth, bring to a boil, reduce heat and simmer until reduced slightly, about 5 minutes. Adjust seasoning with salt and black pepper. If the soup is too sweet, add a splash of white wine. Keep warm.
Preheat broiler. Arrange the baguette slices on a baking sheet in a single layer. Top the bread with cheese. Broil until melted and beginning to brown, 3 to 5 minutes.
To serve, ladle into bowls and top with cheesy croutons. Alternately, toast the bread at 325 degrees for 15 to 20 minutes, turning once. Place the croutons over the soup, sprinkle with cheese and bake at 350 degrees for 20 to 25 minutes or until the cheese is melted and bubbly, then broil briefly to brown the cheese. Serve immediately.