Ingredients :
For the Onions
3 large onions, thinly sliced, about 6 cups
2 large cloves garlic, minced
1 large bay leaf
1 tablespoon unsalted butter
1 tablespoon balsamic vinegar
2 teaspoons Worcestershire sauce
1 teaspoon fine salt
Freshly ground black pepper, to taste
For the Meatballs
1 1/2 pounds lean ground beef (85/15 or 90/10)
1/2 cup panko breadcrumbs
1 packet (1 ounce) dry onion soup mix
1 large egg
1/2 teaspoon herbes de Provence or dried thyme
For the Sauce and Finishing
1 (10.5-ounce) can condensed French onion soup
1 cup unsalted beef broth or water
1/2 teaspoon herbes de Provence or dried thyme
1 1/2 to 2 cups (6 to 8 ounces) shredded Gruyère or Swiss cheese
Fresh thyme leaves or fresh chopped parsley, for garnish, optional
1 baguette, sliced and toasted
Steps to Make It
Gather the ingredients.
Combine 3 large onions, thinly sliced (about 6 cups), 2 large cloves garlic, minced, 1 large bay leaf, 1 tablespoon unsalted butter, 1 tablespoon balsamic vinegar, 2 teaspoons Worcestershire sauce, 1 teaspoon fine salt, and freshly ground black pepper to taste in a large slow cooker and give everything a stir to combine. Cover and cook on high for 3 hours, stirring again after 1 hour.
An insert of a slow cooker with sliced onions, minced garlic, a bay leaf, butter, 1balsamic vinegar, Worcestershire sauce, salt, and pepper
The Spruce Eats / Cara Cormack
About 25 minutes before the 3 hours is up, prepare the meatballs. Position a rack in the center of the oven and heat to 425 F. Line a large rimmed baking sheet with foil.
In a large bowl, combine 1 1/2 pounds lean ground beef (85/15 or 90/10) with 1/2 cup panko breadcrumbs, 1 packet (1 ounce) dry onion soup mix, 1 large egg, and 1/2 teaspoon herbes de Provence or dried thyme.
A large glass bowl with ground beef, panko breadcrumbs, onion soup mix, egg, and herbes de Provence
The Spruce Eats / Cara Cormack
Mix until the ingredients are combined (but do not overmix) and using 2 tablespoons or a 2-tablespoon portion scoop, shape the mixture into 24 to 28 1-ounce meatballs and place on the prepared baking sheet.
A foil-lined baking sheet lined with beef-french onion meatballs
The Spruce Eats / Cara Cormack
Bake the meatballs in the oven for 10 minutes.
A foil-lined baking sheet of baked beef-french onion meatballs
The Spruce Eats / Cara Cormack
Add the meatballs, 1 can (10.5 ounces) condensed French onion soup, 1 cup unsalted beef broth or water, and 1/2 teaspoon herbes de Provence or dried thyme to the slow cooker.
A slow cooker insert with meatballs, condensed French onion soup, beef broth, and herbes de Provence added to the sliced onion mix
The Spruce Eats / Cara Cormack
Cover and cook on high for 2 hours. Taste and adjust the seasonings. Turn the slow cooker to warm until it’s time to serve the meatballs.
A slow cooker insert with French onion meatballs
The Spruce Eats / Cara Cormack
Just before serving, sprinkle the meatballs evenly with 1 1/2 to 2 cups (6 to 8 ounces) shredded Gruyère cheese. Cover and let the
meatballs stand until the cheese is melted, 5 to 10 minutes.
A slow cooker insert with French onion meatballs topped with shredded Gruyère cheese
The Spruce Eats / Cara Cormack
Garnish the meatballs with fresh thyme leaves or chopped parsley if desired, and serve them with 1 baguette, sliced and toasted.
Prep: 20 mins Cook: 5 hrs 10 mins Total: 5 hrs 30 mins Servings: 4 to 6 servings Yield: 24 meatballs