Gourmet Caramelized Onion Soup au Gratin
Indulge in the rich, sweet flavors of our Gourmet Caramelized Onion Soup au Gratin, a classic recipe elevated with velvety texture and topped with golden, bubbly Gruyère cheese. This soup features slow-cooked Spanish onions, perfectly caramelized for deep flavor, simmered in a savory broth of beef stock with hints of cognac and sherry. Finished with crispy sourdough bread and a cheesy crust, each hearty serving is garnished with fresh chives, making it a perfect dish for cold-weather comfort or an elegant dinner party. Serve it warm and enjoy the delightful melding of flavors and textures, a true French classic to share with family and friends.
6
Servings
N/A
Calories
21
Ingredients
Ingredients
Spanish onions
1 1/2-2 lbs (sliced into 1/4 inch slices)
Unsalted butter
2 tablespoons (melted)
Vegetable oil
1 tablespoon (for sautéing)
Kosher salt
1 teaspoon
Brown sugar
3/4 teaspoon (pack lightly)
Garlic cloves
2 (mashed)
All-purpose flour
3 tablespoons
Cognac
1/4 cup
Dry sherry
1/4 cup
Dry red or white wine
1/2 cup
Beef stock
6 cups
Bay leaves
2
Fresh thyme
1 sprig
Ground sage
1/4 teaspoon
Ground black pepper
1/8 teaspoon
Ground white pepper
1/8 teaspoon
Parmesan cheese
to taste (grated)
French sourdough baguette
as needed (sliced)
Olive oil
as needed (for drizzling)
Gruyère cheese
6 ounces (shredded)
Fresh chives
to garnish (snipped)
Instructions
1
Begin by preparing the onions. Cut the ends off the Spanish onions, peel the outer layers, and slice them into 1/4-inch thick rounds.
2
In a heavy-bottomed soup pot, heat the unsalted butter and vegetable oil over medium-low heat. Add the sliced onions, cover, and sauté for about 20 minutes until they are softened.
3
Once the onions are softened, add the kosher salt and brown sugar to enhance their sweetness. Increase the heat to medium-high and stir frequently until the onions are deeply caramelized and golden brown.
4
Add the mashed garlic cloves and continue to stir for one minute to cook the garlic and release its fragrance.
5
Reduce the heat back to medium-low and sprinkle the flour over the onion mixture. Stir well and cook for an additional 2 minutes to remove the raw flour taste.
6
Deglaze the pan by adding the cognac and dry sherry, scraping the bottom to release any caramelized bits. Allow it to simmer uncovered for about 5 minutes.
7
Next, stir in the wine and let the mixture simmer uncovered for 15 minutes, allowing flavors to meld together.
8
Add the beef stock, bay leaves, thyme, ground sage, black pepper, and white pepper. Bring to a simmer and cook uncovered for at least 30 minutes.
9
After simmering, remove the bay leaves and thyme sprig. Adjust seasoning with grated parmesan cheese and kosher salt to taste.
10
While the soup simmers, prepare the sourdough baguette. Slice the baguette into 1/2 to 3/4-inch thick slices. Drizzle both sides of each slice with olive oil and arrange them on a baking sheet.
11
Bake the bread in a preheated oven at 325°F for 15 minutes, then flip the croutes over and continue baking for another 10-15 minutes until they are very crispy.
12
Once the bread is ready, set your broiler to high. Ladle the hot soup into four oven-safe bowls, arrange the crispy baguette slices on top, and generously cover each with shredded Gruyère cheese.
13
Carefully place the bowls under the broiler for 45 seconds to 1 1/2 minutes, watching closely until the cheese melts and bubbles up.
14
Remove the bowls from the oven, sprinkle with additional grated parmesan cheese and fresh chives if desired. Serve hot and enjoy!
Nutrition Information
Frequently Asked Questions
Frequently Asked Questions
What is Gourmet Caramelized Onion Soup au Gratin?
It is a classic French soup featuring slow-cooked Spanish onions in a savory beef stock, topped with toasted sourdough bread and melted Gruyere cheese.
How many servings does this recipe provide?
This recipe yields 6 servings.
What kind of onions should I use for this soup?
The recipe calls for 1.5 to 2 pounds of Spanish onions.
How should the onions be sliced?
The onions should be sliced into 1/4-inch thick rounds.
Why is brown sugar added to the onions?
Brown sugar is added once the onions have softened to enhance their natural sweetness and aid in the caramelization process.
What is the initial sautéing time for the onions?
The onions should be sautéed covered over medium-low heat for about 20 minutes until they are softened.
How do I know when the onions are finished caramelizing?
The onions are ready when they have turned a deep caramelized golden brown color.
What is the purpose of adding flour to the onion mixture?
The flour helps thicken the soup; it should be cooked for 2 minutes to remove any raw flour taste.
What liquids are used to deglaze the pan?
The pan is deglazed using a combination of 1/4 cup cognac and 1/4 cup dry sherry.
What type of wine is recommended for this recipe?
You can use 1/2 cup of either dry red or dry white wine.
How long should the soup simmer after adding the beef stock?
The soup should simmer uncovered for at least 30 minutes after adding the beef stock and herbs.
Which herbs are used to flavor the broth?
The broth is flavored with bay leaves, a fresh thyme sprig, and ground sage.
When should I remove the bay leaves and thyme?
Remove the bay leaves and the thyme sprig after the 30-minute simmer is complete and before assembling the bowls.
What kind of bread is used for the 'au gratin' topping?
A French sourdough baguette is recommended for the bread slices.
How thick should the baguette slices be?
Slice the baguette into 1/2 to 3/4-inch thick slices.
What is the baking temperature for the sourdough croûtes?
The bread should be baked in a preheated oven at 325°F.
How long does the bread take to get crispy in the oven?
Bake for 15 minutes, then flip and bake for another 10 to 15 minutes until very crispy.
What type of cheese provides the classic bubbly crust?
Shredded Gruyere cheese is used as the primary topping, supplemented with grated Parmesan.
Do I need special bowls for this recipe?
Yes, you must use oven-safe bowls to safely melt the cheese under the broiler.
How long should the soup stay under the broiler?
Broil the soup bowls for 45 seconds to 1.5 minutes until the cheese is melted and bubbling.
What is the final garnish for the soup?
The soup is garnished with snipped fresh chives and an extra sprinkle of Parmesan cheese.
Can I use salted butter instead of unsalted?
Yes, but you should adjust the amount of added kosher salt later to prevent the soup from becoming too salty.
Why is vegetable oil mixed with the butter for sautéing?
Vegetable oil has a higher smoke point, which helps prevent the butter from burning during the long onion cooking process.
How much beef stock is required?
The recipe requires 6 cups of beef stock.
What spices are included in the seasoning?
The recipe uses kosher salt, ground black pepper, and ground white pepper.
Can I substitute the cognac?
Brandy is the most suitable substitute for cognac in this recipe.
How should the garlic be prepared?
The 2 garlic cloves should be mashed before being added to the onions.
Is the soup served hot or cold?
The soup should be served hot immediately after the cheese has been broiled.
Can I make the soup base in advance?
Yes, you can prepare the onion soup base ahead of time and perform the bread toasting and cheese broiling steps just before serving.
What defines this soup as 'au Gratin'?
The 'au gratin' designation refers to the technique of topping the dish with bread and cheese and browning it under a broiler.