Leftovers Onion Soup

I love an onion soup! Especially when it’s made from leftovers. There’s a profound satisfaction in utilizing every ingredient in the refrigerator, minimizing food waste. If you have leftover au jus, beef, potatoes, cooked broccoli, carrots, or mushrooms, they will elevate the onion soup recipe outlined below.

When measuring your broth, be sure to incorporate any leftover liquids; this will help you avoid a soup that is overly watery. It's essential to gauge the amount of broth you'll need while incorporating your leftovers.

  • To achieve truly caramelized onions, it's essential to cook them slowly over low heat for about one hour until they reach a deep, dark brown hue.

    If you opt to caramelize for one hour, aim to engage in about 45 minutes of intermittent stirring, followed by the final 15 minutes where you must closely supervise and stir frequently.

    However, for this recipe, a lighter caramelization can be accomplished in just 30 minutes, which will still provide a delightful sweetness.

    For a deeper flavor, consider using a dark beer.

    I enjoy preparing this recipe using Christmas ales or Guinness beer, which adds a unique depth of flavor. The rich, malty notes from these beverages meld beautifully with the other ingredients.

  • Allow older children to assist with slicing the bread and garnishing the bowls with cheese for a fun cooking experience.

    This is an excellent opportunity to introduce your children to the fundamentals of making a simple roux. In this recipe, we are using flour to thicken but we are not making a true roux since we are not using milk. When your child adds the flour, take a moment to explain the role of flour, as well as other thickening agents, in thickening the texture of soups and sauces. Encourage them to experiment with different ingredients and ratios to discover how they can master the art of thickening, creating rich and flavorful dishes in the process.

    This hands-on experience builds cooking skills and helps kids learn the science of cooking, creating a valuable family time in the kitchen.

    With the younger kiddos, we love watching the cheese bubble up & achieve its golden look!

This is a simple, yet delicious beer infused onion soup, adding the leftovers is optional but highly encouraged!

Ingredients:

  • 3 large OR 4 smaller onions (yellow or white), thinly sliced- not chopped, sliced.

  • 2 tablespoons unsalted butter

  • 2 cloves garlic, minced

  • 1 teaspoon sugar

  • 1/2 teaspoon salt

  • 1/4 teaspoon black pepper

  • 1 tablespoon all-purpose flour

  • 6 cups of beef or vegetable broth

  • 1 1/2 cup beer (a lager or ale works well)

  • 2 teaspoon Worcestershire sauce

  • 1 baguette, sourdough or crusty bread, sliced & cubed

  • 2 cups of a mix of shredded Gruyère cheese. You can also use a blend of parmesan and mozzarella and Swiss cheese.

  • Fresh thyme sprigs (optional for garnish)

Steps:

  1. Sauté the Onions: In a large pot, heat the butter over medium heat. Add the sliced onions. Cook for about 20-30 minutes, stirring frequently, until the onions are caramelized and golden brown. If they are starting to stick to the bottom of the pan, add 1 to 2 tablespoons of water.You can expedite the process by covering the pot with a lid for the first 10 minutes. Be sure to stir occasionally, even while it is covered, to ensure even cooking and prevent sticking.

  2. Add Garlic: Stir in the minced garlic and cook for another 1-2 minutes until fragrant.

  3. Thicken the Soup: Sprinkle the flour over the onions, sugar, salt, and pepper, mixing well to incorporate. Cook for 2-3 minutes to remove the raw flour taste.

  4. Deglaze with Beer: Add the Worcestershire sauce, pour in the beer and scrape any browned bits from the bottom of the pot. Allow the beer to simmer for about 5 minutes.

  5. Add Broth: Gradually add the broth, stirring to combine. Bring the mixture to a boil, then reduce the heat and let it simmer for 15-20 minutes.

  6. Prepare the Bread: While the soup is simmering, preheat your oven to 350°F (175°C). Arrange the sliced baguette on a baking sheet, and toast in the oven for about 10 minutes, or until golden brown. This step is optional, but it enhances the structural integrity of your bread, ensuring it holds up beautifully without breaking apart quickly in the soup, giving you perfect bites until the end.

  7. Assemble and Broil: Ladle the soup into oven-safe bowls or ramequins. Place the toasted bread on top of each bowl and generously sprinkle with the mix of Gruyère cheese. Place the bowls under the broiler for about 2 minutes, or until the cheese is bubbly and golden.

  8. Serve: Remove the bowls from the oven carefully. Garnish with fresh thyme if desired and serve hot.

How to store:

Before storing, allow the onion soup to cool to room temperature. This prevents condensation and maintains the soup's texture. If you've made a large batch, consider portioning the soup into smaller containers. This makes it easier to reheat only what you need, minimizing waste. See my favorite containers bellow, they are oven-safe, microwave-safe & dishwasher safe! For short-term storage, place the cooled soup in the refrigerator. It can be stored for up to 3 to 4 days. Make sure to label the container with the date for easy reference. The soup can be stored in the freezer for up to 3 months.

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