Ingredients:
- 2 tablespoons unsalted butter, melted
- 3 pounds yellow onions, thinly sliced (6 medium onions)
- 4 garlic cloves, minced (about 4 teaspoons)
- 1 tablespoon fresh thyme leaves or 1 teaspoon dried thyme
- 1 ½ teaspoons kosher salt, plus additional to taste
- ¼ teaspoon ground black pepper
- 4 cups low-sodium beef broth (1 quart)
- ½ cup dry white wine such as Sauvignon Blanc
- 8-12 slices French bread, 1/4-inch thick
- 3 tablespoons olive oil
- ½ cup shredded Gruyere cheese
Directions:
- In a 6-quart slow cooker, combine the butter, onions, garlic, thyme, salt and pepper. Cover and cook on high for 5 to 7 hours, stirring occasionally, until the onions are caramelized.
- Stir in the broth and wine. Cover and cook on high for 30 additional minutes.
- Meanwhile, place a rack in the upper third position of the oven (about 6 inches from the top) and preheat the broiler. Arrange the bread slices on a baking sheet. Brush both sides with the oil and place under the broiler for 2 to 3 minutes per side, keeping a close eye on them and rotating the pan to avoid burning. Remove from the oven.
- When the soup is done, divide it between 4 oven-safe bowls or ramekins. Place 2 or 3 baguette slices on top of each ramekin and sprinkle about 2 tablespoons of cheese on top of each.
- Place the bowls on a baking sheet and broil for about 2 minutes, until browned and bubbling, keeping a close eye on them under the broiler. Sprinkle with a pinch of salt and pepper and serve.