Ingredients
For the Meatballs:
- 1 lb ground beef
- ½ lb ground pork (or use all beef)
- ½ cup bread crumbs
- ¼ cup grated Parmesan cheese
- 1 large egg
- 1 teaspoon garlic powder
- ½ teaspoon onion powder
- ½ teaspoon salt
- ¼ teaspoon black pepper
- 1 teaspoon Worcestershire sauce
For the French Onion Sauce:
- 2 large onions, thinly sliced
- 3 tablespoons butter
- 1 tablespoon olive oil
- 2 teaspoons brown sugar (to help caramelize the onions)
- 3 cloves garlic, minced
- ½ teaspoon thyme
- 4 cups beef broth
- 1 tablespoon Worcestershire sauce
- 1 teaspoon balsamic vinegar (optional, for depth of flavor)
- 1 tablespoon cornstarch + 2 tablespoons water (to thicken)
- 1 ½ cups grated Gruyère cheese (or Swiss/Mozzarella)
- 2 tablespoons fresh parsley, chopped (for garnish)
Instructions
1. Caramelize the Onions
- In a large skillet, melt butter and olive oil over medium heat.
- Add sliced onions, sprinkle with brown sugar, and cook for 20-25 minutes, stirring occasionally until deep golden brown.
- Stir in garlic and thyme, cook for 1 minute, then transfer onions to the slow cooker.
2. Make the Meatballs
- In a bowl, mix ground beef, ground pork, bread crumbs, Parmesan, egg, garlic powder, onion powder, salt, pepper, and Worcestershire sauce.
- Roll into 1 ½-inch meatballs (about 20 meatballs).
- Brown them in a skillet with a little olive oil for 2-3 minutes per side (optional but adds extra flavor!).
3. Slow Cook Everything Together
- Add browned meatballs to the slow cooker with the onions.
- Pour in beef broth, Worcestershire sauce, and balsamic vinegar.
- Cover and cook on LOW for 4-6 hours or HIGH for 2-3 hours.
4. Thicken the Sauce & Add Cheese
- In the last 30 minutes, mix cornstarch with water and stir it into the slow cooker to thicken the broth.
- Sprinkle Gruyère cheese over the top and cover until melted.
5. Serve & Enjoy!
- Garnish with fresh parsley and serve warm.
- Pair with crusty bread, mashed potatoes, or over egg noodles!
Notes
Tips for the Best French Onion Meatballs
✅ Caramelize the onions well – They add the best deep, rich flavor.
✅ Use a mix of ground meats – Beef + pork = super juicy meatballs.
✅ Brown the meatballs first – It locks in flavor and prevents them from falling apart.
✅ For extra cheesy goodness – Broil with cheese for 2 minutes before serving.
✅ Let the slow cooker do the work – The longer it simmers, the better the flavors!