Onion Soup Au Gratin
A rich, caramelized onion soup topped with toasted bread and melted Gruyere cheese, perfect for comforting gatherings or as a flavorful starter for special occasions.
Ingredients
Instructions
- Melt butter in a large soup pot.
- Add onions and wilt over medium-low heat, covered, for 10 minutes.
- Stir occasionally and sprinkle sugar over onions; toss to coat.
- Cook uncovered until caramelized, about 10 minutes.
- Season with salt and coarsely ground pepper.
- Add 3 cups of beef stock; simmer uncovered over medium heat for 15 minutes.
- Add remaining 3 cups of beef stock and red wine.
- Cook until rich in taste, about 30 to 40 minutes.
Tips & Substitutions
For a deeper flavor, consider using a mix of yellow and sweet onions. If Gruyere isn't available, Emmental or a sharp cheddar can be great substitutes. Be patient while caramelizing the onions; the longer they cook, the more sweetness and depth they develop. Adding a splash of balsamic vinegar at the end can also enhance the richness of this soup.
Serving Suggestions
Serve hot with toasted French bread placed on top and sprinkled with more Gruyere cheese, then broiled until bubbling. A side salad or a light vinaigrette pairs beautifully with this rich dish. For a hearty meal, consider serving it alongside beef recipes like Gulyas (Hungarian Goulash).
Storage & Reheating
Store leftover onion soup in an airtight container in the refrigerator for up to 3 days. To reheat, warm the soup on the stovetop over low heat, stirring occasionally. If you want to enjoy it au gratin again, top with fresh Gruyere and broil until bubbly and golden.
Nutrition & Diet Analysis (per serving)
Each serving of Onion Soup Au Gratin contains roughly 2419 calories, with 119g protein, 78g carbohydrates, and 181g fat. It is an excellent source of protein (238% of the Daily Value), calcium (154% of the Daily Value), and vitamin A (112% of the Daily Value), and a good source of vitamin D and vitamin C. Note that it is relatively high in sodium, at 2742mg per serving (119% of the Daily Value).
Estimated from ingredients & per-serving nutrition — verify against package labels for allergies or strict diets.
* % Daily Values based on a 2,000 calorie diet (FDA 2020).
Frequently Asked Questions
Can I use vegetable broth instead of beef stock?
Yes, you can substitute vegetable broth for beef stock to make a vegetarian version of this soup. However, keep in mind that the flavor will be milder. To enhance the taste, consider adding a splash of soy sauce or miso paste for depth.
How can I make this soup ahead of time?
You can prepare the soup up to the point of adding the final 3 cups of beef stock and red wine. Cool it completely, then store it in the refrigerator for up to 3 days. Reheat before serving, adding the remaining ingredients just before broiling.
What's the best way to caramelize the onions?
Start with medium-low heat and allow the onions to cook slowly. Stir occasionally to prevent sticking, and sprinkle sugar to help with caramelization. If they start to burn, lower the heat further. This process takes time but results in beautifully sweet and deeply flavored onions.
Nutrition is estimated from USDA FoodData Central ingredient data and may vary with brand, portion and preparation — see our methodology. This information is for general educational purposes only and is not medical or dietary advice (disclaimer).