Description
A rich and comforting Slow Cooker French Onion Soup made with caramelized sweet onions, savory beef broth, and aromatic herbs. Topped with toasted baguette croutons and melted Swiss and Parmesan cheeses, this classic French dish is perfect for a cozy meal with minimal hands-on cooking.
Ingredients
Scale
Soup Ingredients
- 1 stick butter
- 5 sweet yellow onions, sliced (white, yellow, or red onions work too)
- 1 tsp salt
- 1/4 tsp pepper
- 1/4 cup flour
- 64 oz beef broth or beef stock (two 32-oz containers)
- 1 tsp sugar (optional, use if onions aren’t labeled “sweet”)
- 2 tsp minced garlic
- 1/4 tsp dried thyme (not ground)
- 1/4 tsp dried oregano (not ground)
- 1 tsp Worcestershire sauce
- 1 Tbsp balsamic vinegar
- 1 bay leaf
For Serving
- 1 baguette
- Olive oil
- 1 whole garlic clove
- Sliced Swiss cheese (can use provolone or gruyere) – about 2 slices per serving
- Shredded Parmesan cheese – about 1 tablespoon per serving
Instructions
- Caramelize the Onions: In a large skillet set to medium-high heat, add the butter. When the butter is melted, add the sliced onions and sprinkle with salt and pepper. Sauté the onions, stirring often, until they become browned and caramelized, about 10 minutes. Adjust heat to prevent burning.
- Add Flour to Onions: Once onions are caramelized, sprinkle the flour over them and cook for another 2 minutes in the skillet to incorporate the flour for thickening.
- Transfer to Slow Cooker and Add Broth: Add the floured onions to the slow cooker. Pour in the beef broth, then add sugar (if using), minced garlic, thyme, oregano, Worcestershire sauce, balsamic vinegar, and bay leaf. Stir everything thoroughly to combine.
- Slow Cook the Soup: Cover and cook the soup on HIGH for 4 hours or LOW for 8 hours to develop deep flavors. Before serving, remove the bay leaf.
- Make Homemade Croutons: Preheat the oven to 500°F and switch to broil setting. Slice the baguette into 1/4 inch pieces and place them on a sheet pan. Brush each slice with olive oil using a pastry brush. Broil for 3-5 minutes until slices are toasted and browned. Once toasted, rub each slice with the cut side of a garlic clove for added flavor.
- Assemble Soup Bowls: Ladle the French Onion Soup into ovenproof bowls. Place the bowls on a pie tin or sheet pan for easier handling. Top each bowl with the homemade garlic croutons, then layer 1-2 slices of Swiss cheese (or provolone or gruyere) on top, and sprinkle with shredded Parmesan cheese.
- Broil Until Cheese Melts: Place the assembled bowls under the broiler until the cheese melts, becomes bubbly, and starts to brown slightly. Serve hot.
Notes
- Freeze leftover soup without croutons or cheese. Allow to cool completely, then store in freezer bags or containers for up to 3 months.
- Thaw frozen soup overnight in the refrigerator and reheat on the stove or microwave before serving.
- For a vegetarian version, substitute beef broth with vegetable broth.
- Adjust the sugar based on the sweetness of your onions to balance flavors.
- Use ovenproof bowls to safely broil the cheese topping.
Nutrition
- Serving Size: 1 cup
- Calories: 220 kcal
- Sugar: 6 g
- Sodium: 920 mg
- Fat: 12 g
- Saturated Fat: 7 g
- Unsaturated Fat: 4 g
- Trans Fat: 0 g
- Carbohydrates: 19 g
- Fiber: 2 g
- Protein: 7 g
- Cholesterol: 30 mg
