Slow Cooker French Onion Soup
We just can't find anything not to love about a good bowl of onion soup, and this recipe happens to be one of our favorite versions. A trip through the slow cooker ensures a deep, rich flavor that is just out of this world. Try this soup as a starter for your next holiday dinner; your guests will not be disappointed! This recipe makes 8 servings.
15 minutes
6 hours / 0 mins
Slow Cooker French Onion Soup
2 large red onions, peeled and thinly sliced into half-moons
3 large yellow onions, peeled and thinly sliced into half-moons
1 large white onions, peeled and thinly sliced into half-moons
3 shallots, peeled and thinly sliced
3 cloves garlic, minced
3 tablespoons olive oil
1/2 cup dry white wine or dry sherry
2 tablespoons brandy
8 cups good-quality beef stock (we like Kitchen Basics brand), brought to room temperature
1 tablespoon flour
1 bay leaf
Leaves from 3-4 sprigs fresh thyme
Kosher salt and pepper
8 1" thick slices of French bread
8 ounces Gruyere cheese, shredded
2 tablespoons butter
Heat a large, heavy skillet to medium-high and add olive oil. Add all onions and shallots and cook, stirring every few minutes, until the onions are softened and beginning to turn a deep, golden color. This process should take about 30 minutes. Add garlic and cook for two more minutes. Season with salt and pepper.

Sprinkle flour over onions, stir to combine and cook for one more minute. Add wine or sherry and brandy and cook until liquid is reduced by half. NOTE: if you are using a gas range, turn off the flame before adding the brandy as it is highly flammable and you do not want to start a fire. Once brandy has been added, turn flame back on and continue to cook.

Once liquid has reduced, turn off heat and add onion mixture to your slow cooker along with the stock, bay leaf and thyme. Cook on low for 4-5 hours. Taste soup and season with salt and pepper, if necessary.

To finish, ladle about a cup of soup into an oven-proof crock. Butter one slice of bread, place on top of soup and top with an ounce of cheese. Repeat with remaining servings. Place crock on a baking sheet and broil until cheese is melted, about five minutes. Serve immediately.
Looking for inspiration? Try these recipes:
Tzatziki Sauce
Tzatziki Sauce
Open-faced Roast Beef Sandwiches
Open-faced Roast Beef Sandwiches
Slow Cooker Pulled Pork Sandwiches with Pickled Red Onions
Slow Cooker Pulled Pork Sandwiches with Pickled Red Onions