My husband is addicted to this idea. We wrap up eating 1 serving and he speedily orders another helping

1 tablespoon olive oil
2 large onions, thinly sliced
1 teaspoon sugar
1 teaspoon balsamic vinegar
1.5 pounds ground beef
3/4 cup breadcrumbs
1 large egg
1 teaspoon thyme, dried
1/2 teaspoon garlic powder
Salt and pepper, to taste
1 cup beef broth
1 cup shredded Gruyère cheese
Directions
1. In a skillet over medium heat, heat the olive oil and add sliced onions. Sprinkle with sugar and cook, stirring occasionally, until onions are caramelized, about 15-20 minutes. Add balsamic vinegar and cook for another 2 minutes.
2. In a large bowl, combine ground beef, breadcrumbs, egg, thyme, garlic powder, salt, and pepper. Mix until well combined.
3. Form the mixture into meatballs, each about the size of a golf ball.
4. Place half of the caramelized onions in a slow cooker. Arrange the meatballs on top, then cover with the remaining onions.
5. Pour beef broth over the meatballs and onions.
6. Cover and cook on low for 6 hours or on high for 3 hours.
7. Sprinkle Gruyère cheese over the meatballs about 10 minutes before serving to allow it to melt.
8. Serve warm and revel in the rich, oniony goodness!
Variations & Tips
For an extra layer of flavor, you could add some mushrooms along with the onions while caramelizing. A little splash of red wine in the beef broth can also enhance the depth of the sauce. If you’re serving to a more adventurous crowd, a pinch of smoked paprika in the meatballs can add a lovely smokiness.