Ingredients
- 6 tablespoons unsalted butter
- 3.5 pounds onions, halved and sliced thin
- 2 teaspoons table salt, divided
- 1 teaspoon sugar
- 1 cup dry red wine
- 8 cups beef broth
- 3 sprigs fresh thyme
- 2 bay leaves
- 1 teaspoon pepper, divided
- 6 ounces baguette, cut into 1-inch cubes
- 3 tablespoons extra-virgin olive oil
- 8 ounces Gruyère cheese, shredded (2 cups)
- 2 ounces Parmesan cheese, shredded (2/3 cup)
Preparation Tips
Caramelizing the onions correctly takes time. Expect this process to take roughly 55 to 70 minutes.
If you do not have oven-safe soup crocks, arrange six piles of croutons on a baking sheet. Cover with cheese and broil on the middle oven rack until the cheese melts, about 1 to 3 minutes. Then, use a spatula to transfer them to individual bowls of soup.
Caramelize the Onions
In a Dutch oven over medium-high heat, melt the butter. Add the onions, 1.5 teaspoons of salt, and the sugar. Cover the pot and cook, stirring occasionally, until the onions become translucent, which takes about 20 minutes.
Uncover the pot and continue to cook until the liquid evaporates and browned bits start to form, around 5 to 10 minutes. Reduce the heat to medium, continue to cook uncovered, stirring frequently, and scraping up the browned bits, until the onions are deeply caramelized, about 30 to 40 minutes. If scorching occurs, lower the heat.
Build the Soup
Stir the wine into the caramelized onions, making sure to scrape up any remaining browned bits from the pot. Cook until the wine is nearly evaporated, approximately 1 minute.
Add the beef broth, thyme sprigs, bay leaves, 3/4 teaspoon of pepper, and additional salt to taste. Bring the soup to a boil over high heat, then reduce to medium-low and simmer uncovered for 30 minutes.
Make the Croutons
Preheat the oven to 350°F and position the rack in the middle. Toss the baguette pieces with the olive oil, a pinch of salt, and some pepper. Spread the pieces on a rimmed baking sheet and bake until they are golden and crisp, which takes about 15 to 18 minutes.
Remove the croutons from the oven and set them aside. Increase the oven temperature to 500°F.
Assemble and Bake
Place six 12-ounce oven-safe crocks on a rimmed baking sheet. Remove the thyme sprigs and bay leaves from the soup, then season the soup to taste.
Distribute the soup evenly among the crocks. Sprinkle a portion of the Gruyère cheese over each crock, add the croutons, and then top with the remaining Gruyère and Parmesan cheeses.
Bake the crocks until the cheese is melted and the soup is bubbling, about 5 to 7 minutes. Allow them to cool for 5 minutes before serving.
Slow Cooker French Onion Soup
Ingredients
- 6 tablespoons unsalted butter
- 3.5 pounds onions halved and sliced thin
- 2 teaspoons table salt divided
- 1 teaspoon sugar
- 1 cup dry red wine
- 8 cups beef broth
- 3 sprigs fresh thyme
- 2 bay leaves
- 1 teaspoon pepper divided
- 6 ounces baguette cut into 1-inch cubes
- 3 tablespoons extra-virgin olive oil
- 8 ounces Gruyère cheese shredded (2 cups)
- 2 ounces Parmesan cheese shredded (2/3 cup)
Instructions
- In a Dutch oven, melt butter over medium-high heat. Add onions, 1.5 tsp salt, and sugar. Cover and cook, stirring occasionally until onions are translucent, about 20 minutes.
- Uncover, cook until liquid evaporates and browned bits form, 5-10 minutes. Reduce heat to medium, cook uncovered, stirring and scraping browned bits until onions are deeply caramelized, 30-40 minutes.
- Stir in wine, scraping browned bits, cook until nearly evaporated, about 1 minute. Add beef broth, thyme, bay leaves, 3/4 tsp pepper, adjust salt. Bring to a boil, reduce to medium-low, simmer uncovered, 30 minutes.
- Preheat oven to 350°F, middle rack. Toss baguette pieces with olive oil, salt, and pepper. Spread on baking sheet, bake until golden and crisp, 15-18 minutes. Remove, set aside. Increase oven to 500°F.
- Remove thyme and bay leaves, season soup to taste. Divide soup among six 12-ounce oven-safe crocks on a baking sheet. Sprinkle with half the Gruyère, add croutons, top with remaining Gruyère and Parmesan.
- Bake until cheese melts and soup bubbles, 5-7 minutes. Cool 5 minutes before serving.