Leftover French Onion Soup
Corey Wong
Total Cost: ~$10.50 | Serves: 4 | Time: 50–60 mins
French onion soup always felt like one of those dishes that takes all afternoon, but it's surprisingly simple once you're patient enough to let the onions caramelize. I made this version using leftover onions from previous H-Mart recipes, topped each bowl with a toasted Lidl bagel instead of traditional French bread, and finished it with melted mozzarella. It's cozy, rich, and a great way to use up ingredients that might otherwise go to waste.
Ingredients + Where I Got Them
| Ingredient | Store | Cost |
|---|---|---|
| Yellow onions (4–5 large, leftover) | H-Mart | ~$3.00 |
| Beef stock (32 oz) | Lidl | ~$2.29 |
| Plain bagels (1 pack) | Lidl | ~$2.49 |
| Block mozzarella cheese | Lidl | ~$2.99 |
| Butter or cooking oil | Pantry | Minimal |
| Salt & black pepper | Pantry | Minimal |
Note: This recipe is perfect for using up onions left over from other meals. You'll also only use a portion of the bagels and mozzarella, so both can be used for future recipes.
Instructions
Caramelize the Onions
Thinly slice the onions.
Heat a large pot over medium heat with a tablespoon of butter or oil.
Add the onions along with a pinch of salt.
Cook slowly for 30–40 minutes, stirring every few minutes, until the onions become deeply golden brown and jammy. Don't rush this step—the caramelized onions are what give the soup its rich flavor.
Make the Soup
Pour in the beef stock.
Stir well, scraping up any browned bits from the bottom of the pot.
Bring to a gentle simmer and cook for another 10–15 minutes so the flavors come together.
Season with black pepper and additional salt if needed.
Prepare the Bagel Topping
Slice a bagel in half and toast until lightly crisp.
Cut the toasted bagel into pieces that fit on top of each ramekin or oven-safe bowl.
Slice or shred the mozzarella cheese.
Assemble
Ladle the soup into oven-safe ramekins.
Place the toasted bagel pieces on top of each bowl.
Cover generously with mozzarella cheese.
Broil for 2–4 minutes, or until the cheese is melted, bubbling, and lightly browned.
Serve immediately while hot.
Price Breakdown (Per Serving)
- Onions: ~$0.75
- Beef stock: ~$0.57
- Bagel: ~$0.31
- Mozzarella: ~$0.75
Total per serving: ~$2.40
Final Thoughts
This has become one of my favorite ways to turn leftover ingredients into something that feels surprisingly elegant. The slow-caramelized onions create a deep, savory broth, while the toasted bagel and melted mozzarella provide all the comforting qualities of classic French onion soup using ingredients I already had on hand. It's proof that a little patience—and a few pantry staples—can transform leftovers into a cozy, café-worthy meal without spending much at all.
