Making this delicious Slow Cooker French Onion Soup is a breeze! Just follow these steps to create a fantastic meal:

1. Prepare the Onions:
– Slice the onions thinly. A mandoline can be helpful for even slices.

2. Sauté the Onions:
– In a large skillet, melt the butter and olive oil over medium heat.
– Add the sliced onions, salt, and sugar. Sauté for about 10 minutes until they start to soften.

3. Add Garlic and Caramelize:
– Add minced garlic to the onions and sauté for another 5-10 minutes, stirring frequently until they are beautifully caramelized.

4. Transfer to Slow Cooker:
– Transfer the caramelized onion mixture to your slow cooker.

5. Add Broth and Herbs:
– Pour in the beef or vegetable broth. If using wine, add it here too.
– Stir in the thyme, bay leaves, and black pepper.

6. Set Slow Cooker:
– Cover the slow cooker and set it to cook on low for 6-8 hours or high for 4-5 hours.

7. Taste and Adjust Seasonings:
– Once the cooking time is complete, taste the soup and adjust the seasoning with more salt and pepper if necessary.

8. Prepare the Bread:
– In the last 10-15 minutes of cooking, preheat your oven to broil.
– Place the baguette slices on a baking sheet and toast them under the broiler until golden brown, about 2-3 minutes.

9. Serve the Soup:
– Remove the bay leaves from the soup and ladle servings into oven-safe bowls.
– Place a slice of toasted bread on each serving and generously sprinkle with Gruyère and Parmesan cheese.

10. Broil until Cheese is Bubbling:
– Place the bowls on a baking sheet and broil in the oven until the cheese is melted and bubbly, about 2-3 minutes.