Caramelized Onion Soup is a rich and comforting dish full of deep, sweet onion flavor that’s been slowly cooked until golden and tender. This soup has a silky broth that feels like a warm hug, and the caramelized onions really make it something special. It’s a classic that’s simple but packed with flavor, perfect whenever you need something cozy.
I love making this soup on chilly evenings when I want to slow down and enjoy something homemade. The key is to be patient while cooking the onions low and slow—that’s where all the magic happens and the sweetness builds up. I always find myself sneaking little tastes as the onions soften, and it never gets old.
One of my favorite ways to serve Caramelized Onion Soup is with a crusty piece of bread topped with melted cheese right on top—it turns the soup into a meal that’s both filling and delicious. It’s also great to share with friends or family when you want something easy but thoughtful. This soup always brings everyone around the table with smiles and full bellies.
Key Ingredients & Substitutions
Yellow Onions: These are the best choice for caramelizing thanks to their natural sweetness and balanced flavor. If you can’t find yellow onions, sweet onions like Vidalia work well too.
Butter and Olive Oil: A combo of butter and olive oil helps brown the onions without burning. You can use all butter for a richer flavor or all oil for a dairy-free option.
Broth: Beef broth adds deep, meaty flavor, but you can use all chicken broth or vegetable broth for a lighter or vegetarian version.
Gruyère Cheese: Perfect for melting and adds nuttiness. Substitute with Swiss cheese or mozzarella if needed, though the flavor will be milder.
White Wine or Sherry: Adds acidity and helps deglaze the pan after caramelizing onions. If you prefer not to use alcohol, you can skip it or replace it with a little extra broth or a splash of vinegar.
How Do You Get Onions Perfectly Caramelized Without Burning Them?
The secret to richly caramelized onions is patience and low heat. Rushing this step will burn the onions or leave them raw-tasting. Here’s how to nail it:
- Cook onions on low to medium heat, stirring often to prevent sticking.
- Add a pinch of sugar to help the natural sugars caramelize faster.
- If they start sticking or browning too quickly, lower the heat and add a splash of water to loosen any bits from the pan.
- Expect this step to take 40-50 minutes; slow cooking brings out the deep sweetness.
Once they’re a deep golden brown and smell sweet, you’re ready for the next step! This patience pays off in the soup’s rich flavor.
Equipment You’ll Need
- Large heavy-bottomed pot or Dutch oven – perfect for slow, even caramelizing of onions without burning.
- Wooden spoon or silicone spatula – gentle on your pot and great for stirring frequently.
- Chef’s knife and cutting board – to slice onions thinly and evenly for consistent cooking.
- Baking sheet – to toast the bread slices under the broiler easily.
- Oven-safe soup bowls or crocks – essential for broiling the soup with cheese on top without breaking.
Flavor Variations & Add-Ins
- Add a splash of sherry or dry white wine for a bright, tangy layer that cuts through the sweetness.
- Use vegetable broth instead of beef for a vegetarian-friendly version with lighter flavor.
- Stir in fresh thyme or rosemary while simmering for extra herb aroma you’ll love.
- Top with different cheeses like mozzarella or fontina for a milder melt and creamier texture.
Caramelized Onion Soup
Ingredients You’ll Need:
For the Soup:
- 6 large yellow onions, thinly sliced
- 4 tablespoons unsalted butter
- 2 tablespoons olive oil
- 1 teaspoon salt
- ½ teaspoon sugar
- 4 cups beef broth (preferably homemade or low sodium)
- 2 cups chicken broth (low sodium)
- ½ cup dry white wine or dry sherry (optional)
- 1 tablespoon balsamic vinegar (optional, for depth)
- 1 teaspoon fresh thyme leaves (or ½ teaspoon dried thyme)
- 1 bay leaf
- Salt and freshly ground black pepper, to taste
For Topping:
- 1 baguette or crusty French bread, sliced
- 2 cups grated Gruyère cheese (or Swiss cheese)
How Much Time Will You Need?
Plan for about 1 hour and 15 minutes total. The most time-intensive task is patiently caramelizing the onions, which takes around 40-50 minutes. Adding the simmering and broiling makes the rest of the time. This slow process brings out incredible flavor!
Step-by-Step Instructions:
1. Caramelize the Onions:
Heat butter and olive oil in a large heavy-bottomed pot or Dutch oven over medium heat. Add the sliced onions, salt, and sugar. Cook gently, stirring often, for 40 to 50 minutes until onions are deeply golden and caramelized. Take your time here to bring out the sweetness.
2. Add Wine and Broth:
If using, pour in the white wine or sherry to deglaze the pot, stirring to scrape up tasty browned bits. Then add beef broth, chicken broth, thyme, and bay leaf. Bring to a boil, then reduce heat and simmer uncovered for 30 minutes. Stir occasionally.
3. Prepare the Bread and Cheese:
While the soup simmers, preheat your oven’s broiler. Arrange bread slices on a baking sheet and toast under the broiler until golden brown on both sides, about 1-2 minutes per side. Remove the bay leaf from the soup and season with salt, pepper, and balsamic vinegar to taste.
4. Assemble and Broil:
Ladle the hot soup into oven-safe crocks or bowls. Place one or two toasted bread slices on top, then sprinkle generously with grated Gruyère cheese. Place bowls on a baking sheet and broil in the oven until cheese melts, bubbles, and browns (3-5 minutes). Watch carefully to avoid burning.
5. Serve:
Optionally garnish with fresh thyme, then serve immediately to enjoy the warm, rich flavors of this comforting soup.
Can I Use Frozen Onions for This Soup?
It’s best to use fresh onions for caramelizing because frozen onions release extra water and won’t brown as well. If you must use frozen, thaw them completely and drain any excess moisture before cooking.
Can I Make This Soup Ahead of Time?
Yes! You can caramelize the onions and prepare the soup base a day ahead. Store it in the fridge and reheat gently before adding the bread and cheese toppings to broil right before serving.
How Should I Store Leftovers?
Keep leftover soup in an airtight container in the fridge for up to 3 days. When reheating, warm on the stove and add fresh bread and cheese toppings to broil again for the best texture.
What Are Good Substitutes for Gruyère Cheese?
Swiss cheese is a great substitute if you can’t find Gruyère. Mozzarella or fontina also work well, though the flavor will be milder and less nutty.
