Ingredients

• 2 pound yellow onions, thinly sliced
• 3 leeks, cleaned and sliced into rings
• 1 pound russet potatoes, peeled and diced
• 4 tablespoon unsalted butter
• 6 cup vegetable broth
• 1 cup dry white wine
• 2 bay leaves
• 2 sprig fresh thyme
• 1 teaspoon salt
• 0.5 teaspoon black pepper
• 0.25 teaspoon ground nutmeg
• 4 slice baguette, cut 1 inch thick
• 1 cup Gruyère cheese, shredded

Steps

1. Clean the leeks thoroughly by slicing them lengthwise, rinsing between layers to remove any sand or soil, then slice into rings about 1/4 inch thick. Set aside.
2. Peel and dice the russet potatoes into 1/2 inch cubes. Place in a bowl of cold water to prevent discoloration and set aside.
3. Melt the butter in a large heavy-bottomed pot over medium-low heat.
4. Add the sliced onions to the melted butter and stir to coat evenly. This is the beginning of the caramelization process.
5. Cook the onions for 40 minutes, stirring frequently (every 5-7 minutes), allowing them to slowly caramelize to a deep golden-brown color. The onions should become very soft and release their natural sugars.
6. Add the cleaned leek rings to the caramelized onions and cook for 3 minutes, stirring occasionally.
7. Pour in the dry white wine to deglaze the pot, scraping up any browned bits from the bottom with a wooden spoon. Simmer for 2 minutes.
8. Add the vegetable broth, drained diced potatoes, bay leaves, and fresh thyme sprigs to the pot.
9. Season with salt, black pepper, and ground nutmeg. Stir well to combine.
10. Bring the soup to a boil over medium-high heat, then reduce to medium and simmer for 15 minutes until the potatoes are tender.
11. While the soup simmers, preheat your oven to 400°F and arrange the baguette slices on a baking sheet.
12. Toast the baguette slices in the preheated oven for 4 minutes until lightly golden and crispy.
13. Remove the bay leaves and thyme sprigs from the soup. Taste and adjust seasoning with additional salt and pepper if needed.
14. Ladle the hot soup into 4 oven-safe bowls or crocks, filling each about three-quarters full.
15. Top each bowl with one toasted baguette slice, then generously cover each slice with 1/4 cup of shredded Gruyère cheese.
16. Place the filled bowls on a baking sheet and transfer to the preheated 400°F oven. Bake for 5 minutes until the cheese is completely melted and lightly golden on top.
17. Carefully remove the hot bowls from the oven (the handles and crocks will be very hot) and let cool for 1 minute before serving.