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–+ servings
Crockpot French Onion Soup 1

Crockpot French Onion Soup

This soul-warming Crockpot French Onion Soup transforms humble ingredients into a rich, caramelized masterpiece while you go about your day. The slow cooker does the heavy lifting, breaking down onions into sweet, tender strands swimming in a savory broth that rivals any French bistro's offering.
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Prep Time 15 minutes
Cook Time 8 hours
Total Time 8 hours 15 minutes
Course Appetizer, Main Course, Soup
Cuisine French
Servings 6 servings
Calories 320 kcal

Equipment

  • Slow Cooker/Crockpot
  • Mandoline (optional)
  • Oven-safe bowls
  • Baking Sheet

Ingredients
  

Soup Base

  • 4 large sweet onions approximately 3 pounds, thinly sliced
  • 3 tablespoons butter
  • 1 tablespoon olive oil
  • 2 tablespoons brown sugar helps with caramelization
  • 2 cloves garlic minced
  • 2 bay leaves
  • 2 sprigs fresh thyme or 1 teaspoon dried thyme
  • 1 tablespoon Worcestershire sauce
  • 1/2 cup dry white wine can substitute with additional beef broth
  • 4 cups beef broth use low-sodium if preferred
  • 2 cups chicken broth creates a more balanced flavor profile
  • 1/2 teaspoon black pepper
  • salt to taste

Cheesy Topping

  • 8 slices French baguette toasted
  • 1 1/2 cups gruyère cheese shredded (can substitute with Swiss cheese)
  • 1/2 cup Parmesan cheese freshly grated

Instructions
 

  • Slice your onions thinly and uniformly (about 1/8 inch thick) to ensure even cooking.
  • Place butter and olive oil in the bottom of your slow cooker. Add the sliced onions, brown sugar, minced garlic, and a pinch of salt.
  • Cover and cook on high for 1 hour to jumpstart the caramelization process.
  • After the first hour, stir the onions well and reduce heat to low. Continue cooking for 6-8 hours, stirring occasionally if possible.
  • Once onions are deeply caramelized, add white wine and let it cook for 10 minutes with the lid off.
  • Add beef broth, chicken broth, Worcestershire sauce, bay leaves, thyme, and pepper. Cover and cook on low for an additional 1-2 hours.
  • While the soup finishes, toast baguette slices until lightly golden. Combine shredded gruyère and Parmesan in a bowl.
  • Ladle soup into oven-safe bowls placed on a baking sheet. Float a slice of toasted baguette on top of each and generously cover with cheese mixture.
  • Broil 6 inches from heat source for 3-4 minutes, or until cheese is bubbly and golden with brown spots.
  • Serve immediately while cheese is hot and melty.

Notes

For a vegetarian version, use vegetable broth instead of beef and chicken broth and add 1 tablespoon of soy sauce or miso paste for depth of flavor.
The soup base (without bread and cheese) can be stored in the refrigerator for up to 5 days or frozen for up to 3 months.
Flavor actually improves after 24 hours as ingredients continue to meld together.
For best results, use a mix of onion varieties for more complex flavor.

Nutrition

Calories: 320kcalCarbohydrates: 24gProtein: 15gFat: 18gSaturated Fat: 9gSodium: 890mgFiber: 3gSugar: 9gCalcium: 25mgIron: 8mg
Keyword French Onion Soup, Crockpot Soup, Slow Cooker Soup, Comfort Food
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