Servings
Font
Back
0 from 18 votes

Slow Cooker French Onion Soup Recipe

Slow cooker French onion soup is the perfect cozy meal that is rich, flavorful, and easy to make. Indulge in a creamy, cheesy masterpiece without the hassle.

Prep Time
10 mins
Cook Time
6 hrs
Total Time
6 hrs 10 mins
Servings: 8
Calories: 188 kcal
Course: Main Course
Cuisine: American

Ingredients

  • 4-5 large sweet onions sliced
  • 4 tablespoons butter sliced into pats
  • 2 tablespoons flour
  • ½ teaspoon salt
  • ¼ teaspoon ground black pepper
  • 1 tablespoon Worcestershire sauce  optional, leave out for a vegetarian recipe
  • ½ teaspoon ground thyme
  • 8 cups broth
  • 4 cups water
  • 2 tablespoons chopped fresh parsley divided
  • french or italian bread sliced into eight slices
  • 4 ounces gruyere cheese shredded

Instructions

    Cup of Yum
  1. Place the onions and flour in the crock of your slow cooker. Use tongs to toss so that the onions are well-coated in the four.
  2. Add the butter pats over the coated onions, then season with salt & pepper.
  3. Place the lid on your slow cooker and let the onions cook on high for 5-6 hours. Stir once every hour to ensure the butter is distributed and the onions are caramelizing and not burning.
  4. When the onions have reached a deep brown, caramelized color, add the Worcestershire sauce and thyme.
  5. Add the beef broth and water and stir to combine.
  6. Continue cooking for another 1-2 hours or until the flavors come together and the soup is heated. Serve in bowls and garnish with fresh parsley.
  7. As described below, make the cheesy toast in either the oven or the air fryer.
  8. Garnish the cheese toasts with additional parsley.
  9. Place one slice of cheese toast in your French onion soup bowl and serve hot.
To make cheese toasts in the oven:
    Cup of Yum
  1. Preheat your oven to 350 degrees F.
  2. Line a baking sheet with parchment paper and arrange the bread slices.
  3. Place a small pile of Gruyere cheese in the center of each slice of bread.
  4. Bake in the oven for 8-10 minutes or until the cheese is melted and just starting to crisp & brown on the edges.
To make cheese toasts in the air fryer:
  1. Arrange the bread slices in the air fryer basket.
  2. Place a small pile of Gruyere cheese in the center of each slice of bread.
  3. Bake in the air fryer at 350 degrees F for 5 minutes or until the cheese is melted and just starting to crisp & brown on the edges.

Notes

  • This is not a "set it and forget it" type of slow cooker recipe, as you do need to be present to stir the onions as they caramelize throughout the day. However, if you prefer, you can caramelize the onions in a skillet first: Melt the butter over medium-high heat and add the sliced onions. Cook for 45-60 minutes, stirring often and sprinkling with salt as they cook, until they caramelize. Add them to the crockpot along with the remaining ingredients and cook on low for 8 hours or on high for 4 hours. 
  • While you can certainly use just one type of onion, you can also use a mix of sweet onions for extra flavor.
  • Beef broth is traditional, but vegetable or mushroom broth works well too.
  • This is not a "set it and forget it" type of slow cooker recipe, as you do need to be present to stir the onions as they caramelize throughout the day. However, if you prefer, you can caramelize the onions in a skillet first: Melt the butter over medium-high heat and add the sliced onions. Cook for 45-60 minutes, stirring often and sprinkling with salt as they cook, until they caramelize. Add them to the crockpot along with the remaining ingredients and cook on low for 8 hours or on high for 4 hours. 
  • While you can certainly use just one type of onion, you can also use a mix of sweet onions for extra flavor.
  • Beef broth is traditional, but vegetable or mushroom broth works well too.

Nutrition Information

Calories 188kcal (9%) Carbohydrates 15g (5%) Protein 9g (18%) Fat 11g (17%) Saturated Fat 7g (35%) Polyunsaturated Fat 0.5g Monounsaturated Fat 3g Trans Fat 0.2g Cholesterol 31mg (10%) Sodium 1232mg (51%) Potassium 366mg (10%) Fiber 2g (8%) Sugar 9g (18%) Vitamin A 400IU (8%) Vitamin C 10mg (11%) Calcium 201mg (20%) Iron 1mg (6%)

Nutrition Facts

Serving: 8Serving

Amount Per Serving

Calories 188

% Daily Value*

Calories 188kcal 9%
Carbohydrates 15g 5%
Protein 9g 18%
Fat 11g 17%
Saturated Fat 7g 35%
Polyunsaturated Fat 0.5g 3%
Monounsaturated Fat 3g 15%
Trans Fat 0.2g 10%
Cholesterol 31mg 10%
Sodium 1232mg 51%
Potassium 366mg 8%
Fiber 2g 8%
Sugar 9g 18%
Vitamin A 400IU 8%
Vitamin C 10mg 11%
Calcium 201mg 20%
Iron 1mg 6%

* Percent Daily Values are based on a 2,000 calorie diet.