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Slow Cooker French Onion Soup Recipe

Slow Cooker French Onion Soup

iamwinfred
This slow cooker French onion soup recipe takes the classic bistro favorite and turns it into a hands-off, set it and forget it meal. Deeply caramelized onions simmer away in a rich beefy broth while you go about your day. By the time you're ready for dinner, all that's left to do is ladle it into bowls, pile on toasted baguette and melty Gruyere, and slide it under the broiler.
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Prep Time 20 minutes
Cook Time 10 hours 30 minutes
Total Time 10 hours 50 minutes
Course Soup
Cuisine French
Servings 6 servings
Calories 420 kcal

Equipment

  • 6-quart slow cooker
  • Sharp chef's knife
  • Cutting board
  • Wooden spoon
  • Ladle
  • Oven safe soup crocks or ramekins
  • Baking sheet
  • Oven with a broiler function

Ingredients
  

  • 3 pounds yellow onions about 6 medium, thinly sliced
  • 4 tablespoons unsalted butter 57g
  • 1 teaspoon salt
  • 1/2 teaspoon black pepper
  • 6 cups beef broth 1.4L, use good quality for best flavor
  • 3 cloves garlic minced
  • 2 sprigs fresh thyme or 1 teaspoon dried thyme
  • 1 bay leaf
  • 1/2 cup dry sherry 118ml, or dry white wine
  • 1 tablespoon Worcestershire sauce
  • 1 French baguette sliced into 1-inch rounds
  • 2 cups Gruyere cheese shredded, 225g
  • 1/2 cup Parmesan cheese grated, optional, 55g

Instructions
 

  • Peel and trim onions, slice into thin even half-moon strips about 1/8 inch thick.
  • Add butter and sliced onions to slow cooker, sprinkle with salt and pepper, stir to coat. Cover and cook on low for 8-9 hours or high for 4-5 hours until deeply golden and jammy.
  • Stir in beef broth, minced garlic, thyme, bay leaf, sherry, and Worcestershire sauce. Cover and cook on low for 2-3 hours to meld flavors.
  • Preheat broiler. Arrange baguette slices on baking sheet and toast 1-2 minutes per side until golden and crisp.
  • Ladle hot soup into oven-safe crocks, top with toasted baguette slices, sprinkle generously with Gruyere and Parmesan. Broil 2-4 minutes until cheese is bubbly and browned. Let cool slightly before serving.

Notes

  • Don't rush the caramelizing step—the long slow cook is where all the flavor develops.
  • Use sweet yellow onions rather than red or white for the most traditional flavor.
  • A good quality beef broth makes a noticeable difference since it's the base of the whole soup.
  • Broil the topped bowls close to the heat source, but watch them constantly so the cheese doesn't burn.
  • Let the soup rest for a couple of minutes after broiling since the crocks retain heat.
  • To make vegetarian: swap beef broth for vegetable broth and skip Worcestershire sauce.
  • Cheese swaps: use Swiss, provolone, or mozzarella in place of Gruyere.
  • Add a splash of balsamic vinegar for extra depth and a touch of sweetness.
  • Store soup base (without bread and cheese) in fridge for up to 4 days or freeze for up to 3 months.
  • Reheat gently and add fresh bread and cheese just before serving.

Nutrition

Serving: 1BowlCalories: 420kcalCarbohydrates: 34gProtein: 22gFat: 22gSaturated Fat: 12gPolyunsaturated Fat: 1gMonounsaturated Fat: 7gCholesterol: 55mgSodium: 980mgPotassium: 450mgFiber: 3gSugar: 8gVitamin A: 10IUVitamin C: 15mgCalcium: 35mgIron: 10mg
Keyword comfort food soup, crockpot french onion soup, easy french onion soup, slow cooker french onion soup
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