Slow-Cooker French Onion Soup with Gruyère Toasts

A white soup bowl filled with French Onion Soup recipe topped with a baguette slice sprinkled with melted Gruyère cheese.

5 from 1 vote

Slow-Cooker French Onion Soup with Gruyère Toasts

This Slow Cooker French Onion Soup gives you all the restaurant-style flavor with just 20 minutes of hands-on time. It's one of those recipes where your kitchen does the work while you get to enjoy the delicious payoff.

Prep Time20

Cook Time12

Total Time12 20

Course: Appetizer soup, main course soup

Cuisine: French

Servings: Servings

Calories: 244kcal

Author: Marisa Franca @ All Our Way

Equipment

Ingredients

10 cups vertically sliced onions from 5 onions
2 tablespoons unsalted butter melted
½ teaspoon black pepper
6 cups unsalted beef stock
¼ cup dry Marsala wine
1 teaspoon chopped fresh thyme plus more for garnish
¾ teaspoon kosher salt
12 ounces whole-wheat baguette see Tip, cut into 16 slices
5 ounces Gruyère cheese shredded (about 1 ¼ cups)

Instructions

Coat a 4-quart slow cooker with cooking spray.
Mix the onions, butter, and pepper in the slow cooker. Cover it and cook on LOW. Cook until the onions are very soft and deep golden brown, which takes about 10 hours.
Stir in the stock, marsala, thyme and salt. Cover and cook on HIGH until the flavors are blended, about 2 hours.
Preheat the broiler with the oven rack 6 inches from the heat.
Place the baguette slices on a baking sheet, and sprinkle evenly with the Gruyère. Broil until the Gruyère melts, 2 to 3 minutes.
Ladle the soup into bowls. Top with the cheese toasts. Garnish with the additional thyme, if desired.

Notes

👩🏻‍🍳 Tips

Day-old bread is perfect for making the cheese bread topping. If you have enough on hand, don't bother about buying a fresh loaf specifically for making this soup.
You can adjust the volume of soup made to suit the size of the slow cooker that you have. I've used a 4-quart slow cooker for this recipe, but you can make a larger serving in a 6-quart slow cooker.
Be sure to spray the slow cooker pot with cooking spray at the start. This will help prevent food from sticking and burning.

Nutrition