Ingredients:
3 pounds of sliced yellow onions
2 tablespoons of melted unsalted butter
2 tablespoons of olive oil
¼ cup of balsamic vinegar
2 fresh thyme twigs
8 cups beef stock
1.5 cups of shredded Gruyere cheese
Salt and pepper to taste
Optional: ⅓ cup of brandy
To serve: A few pieces of crispy bread
Instructions:
1. Place sliced onions in a slow cooker.
2. Add butter, olive oil, salt, and pepper to the slow cooker with the onions.
3. Cover and cook on low for 10-12 hours until the onions are golden and tender.
4. Mix in beef stock, grape-derived vinegar, and fresh thyme leaves.
5. Keep the lid on and cook on low for an additional 6-8 hours. Season with more salt and pepper to taste, and optionally, add brandy.
6. Preheat the oven to 350°F (180°C).
7. Divide the soup into heat-resistant bowls on a baking tray.
8. Top each bowl with a slice of toasted bread and sprinkle with Gruyere cheese.
9. Bake for 20-30 minutes until the cheese melts. Broil for 2-3 minutes until the cheese turns bubbly and brown.

10. Remove, let it cool briefly, and enjoy your French onion soup!
Slow Cooker French Onion Soup is now ready to be enjoyed. The combination of caramelized onions, flavorful broth, and gooey cheese creates a taste sensation that will warm your heart and satisfy your cravings for a comforting meal.