Slow Cooker French Onion Soup
Slow Cooker French Onion Soup is rich, savory comfort food with caramelized onions, a flavorful beef broth, crusty bread, and melty cheese.
Servings 6 servings
Calories 643kcal
Ingredients
- 3 lbs sweet Vidalia onions thinly sliced
- 6 Tbsp unsalted butter or salted butter divided use
- 1-2 Tbsp olive oil
- 3 large garlic cloves minced
- 1 Tbsp light brown sugar
- 1 1/2 Tbsp all purpose flour
- 7 cups low sodium beef stock
- 2 Tbsp worcestershire sauce
- 1-2 Tbsp Kitchen bouquet browning sauce optional
- 2 tsp dried thyme
- 2 large bay leaves
- 2 tsp garlic salt adjust to taste
- 1-2 tsp black pepper adjust to taste
- 1 lb french baguette 1/2-inch slices
- 2 cups shredded Gruyere cheese or aged cheddar cheese
Instructions
- Melt 4 Tbsp butter with the olive oil in a large skillet over medium-high heat. Add the onions, stir to coat with butter mixture then lower the heat to medium-low. Cook uncovered 15–20 minutes, stirring occasionally until softened and beginning to turn golden brown.
- To the onions add the garlic and brown sugar and cook for another 2 minutes. Sprinkle the flour over the onions, and stir to coat.
- Transfer onion mixture to the slow cooker. Pour in the beef stock and Worcestershire sauce, kitchen bouquet (if using) then add the dried thyme, bay leaves, garlic salt and black pepper. Stir to combine.
- Cover with lid and cook on LOW for 7–8 hours or HIGH for 4–5 hours, until the onions are beautifully soft and the soup has a rich flavor.
- Remove the bay leaves, then taste and adjust salt and black pepper. Add more to suit your taste, if needed.
- Make the Gruyere Croutons - Set oven to broil. Slice baguette into 1/2-inch slices. Arrange on a parchment paper lined baking sheet pan. Use the reserved butter to slather each slice. Toast lightly.
- Top croutons with shredded cheese, return to the oven and toast until the cheese is melted, bubbly and golden brown.
- Ladle the soup into bowls and top each serving with cheesy toast.
- Alternate Topping - If you'd like to go classic old school, ladle the french onion soup into oven safe soup crocks or ramekins. Top each with two pieces of buttered toast and sprinkle with Gruyere cheese. Pop under the broiler until the cheese melts.
Notes
- Onions - You can make french onion soup using yellow onions for an even stronger onion taste.
- Even Slicing for Even Cooking - Slice the onions fairly evenly so they soften at a similar rate.
- Caramelizing is Key - Don't rush the initial 15–20 minute cooking time; this helps the onions develop color and flavor before they go into the slow cooker.
- Kitchen Bouquet - This little secret is optional, but adds to the deep dark color and flavor of the soup that makes it so appealing.
- Cheese for French Onion Soup - Gruyère gives the soup a classic finish, while mature Cheddar and sharp Cheddar cheese are both an easy alternative. You could also use mozzarella cheese or swiss cheese.
- Aromatics - Remove the both bay leaves before serving.
- Fresh Herbs - You can use fresh thyme, fresh parsley or chives for garnishing.
- Make the Toast Just Before Serving - Keep the baguette toasts separate until serving so they remain crisp.
Nutrition
Serving: 1serving | Calories: 643kcal | Carbohydrates: 66g | Protein: 28g | Fat: 30g | Saturated Fat: 16g | Polyunsaturated Fat: 2g | Monounsaturated Fat: 10g | Trans Fat: 0.5g | Cholesterol: 79mg | Sodium: 2206mg | Potassium: 971mg | Fiber: 6g | Sugar: 17g | Vitamin A: 793IU | Vitamin C: 18mg | Calcium: 618mg | Iron: 5mg