Slow Cooker French Onion Soup

Course: Soup

Cuisine: American

Diet: Vegetarian

Prep Time: 10

Cook Time: 6 25

Total Time: 6 35

Servings: servings

Calories: 431cal

Author: Ashley Fehr

This Slow Cooker French Onion Soup is made with sweet caramelized onions, savory broth, and melted cheese on top of crispy bread. It's so easy in the slow cooker and perfect for chilly nights!

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Ingredients

1 tablespoon oil
4 large yellow onions
¼ cup salted butter
1 tablespoon brown sugar
1½ teaspoons salt
½ teaspoon dried thyme
¼ teaspoon pepper
⅛ teaspoon red chili flakes
5 cups low sodium beef broth
⅔ cup dry white wine (or sub additional broth)
1 bay leaf
4 thick slices French bread or 8 slices baguette
2 tablespoons salted butter
1 cup shredded cheese (Gruyere, Mozzarella, Gouda, Swiss, Parmesan, Asiago, etc. -- a combination if possible)

Instructions

Heat the oil in a large skillet over medium-high heat.
Slice the onions thinly (I like to cut shorter slices -- from a quarter onion rather than a half -- so they fit more nicely on the soup) and add to the skillet.
Cook and stir until softened and starting to brown, about 10 minutes.
Add the butter, brown sugar, salt, thyme, pepper and red chili flakes. Cook and stir until beginning to caramelize, about 5 minutes.
Place the onions in a 3-4 quart slow cooker and stir in the broth, white wine (or sub broth) and bay leaf. Cook on low for 6-8 hours.
Just before serving, preheat the oven to 425℉. Lightly butter both sides of the bread slices, and place on a parchment lined baking sheet.
Place in the oven and toast for 3-4 minutes, then flip and top each with cheese. I like to use 2-3 cheeses for the best flavor, but the kinds you use are very customizable. If adding hard cheeses, I recommend only a small sprinkling of those along with a good melting cheese.
Bake for 3-4 minutes, until toasted and golden.
Taste soup and adjust seasonings as desired. Ladle into four bowls and top with toasted bread slices. Serve.

Video

Notes

Ingredients and Substitutions:

Onions: you can use a wide variety of onions in this recipe, or a combination. White and Vidalia onions also work well.
Seasonings: you can add in a variety of fresh or dried herbs according to your tastes.
White wine: if using wine, be sure to choose a dry and not a sweet wine. If not using wine, you can substitute for additional beef or chicken broth.

Make ahead:

Refrigerator: you can prep this recipe up to the point of slow cooking, then put the lid on and place it in the refrigerator up to 4 days before slow cooking and topping.
Freezer: this recipe freezes very well without the toasted bread! Simply cook, cool and place in freezer-safe containers (the entire batch or individual servings), then thaw and heat before topping.

Nutrition