Name: Crockpot French Onion Meatballs
Prep time: 25 min
Cook time: 295 min
Total time: 320 min
Yield: 6
Ingredients: 2 pounds frozen fully cooked beef meatballs; 3 large yellow onions, thinly sliced; 3 tablespoons unsalted butter; 2 cups low-sodium beef broth; 1 packet (1 oz) French onion soup mix; 2 tablespoons Worcestershire sauce; 3 cloves garlic, minced; 1 teaspoon dried thyme; ½ teaspoon black pepper; 1 tablespoon brown sugar (optional, for caramelizing onions); 2 tablespoons cornstarch; 2 tablespoons cold water; 1½ cups shredded Gruyère cheese or provolone cheese; ½ cup shredded mozzarella cheese; Fresh parsley or thyme, for garnish

Instructions:

Melt the butter in a large skillet over medium heat. Add the thinly sliced onions and cook, stirring occasionally, for 15 to 20 minutes until they become soft and caramelized to a deep golden brown. Adding brown sugar at this stage will enhance their natural sweetness and help with caramelization.
Add the minced garlic to the caramelized onions and cook for an additional 30 seconds, just until fragrant, to avoid burning the garlic.
Place the frozen, fully cooked beef meatballs in an even layer at the bottom of a 6-quart slow cooker.
Spread the caramelized onions evenly over the meatballs, ensuring each meatball gets a generous coating of the flavorful onion mixture.
In a separate bowl, whisk together the low-sodium beef broth, French onion soup mix, Worcestershire sauce, dried thyme, and black pepper until well combined.
Pour this broth mixture over the meatballs and onions in the slow cooker. Stir gently to coat the meatballs evenly with the sauce without breaking them apart.
Cover the slow cooker and cook on LOW for 4 to 5 hours, allowing the meatballs to heat through thoroughly and the flavors to meld slowly for the best taste and texture.
About 20 minutes before serving, mix the cornstarch with cold water until smooth to create a slurry. Stir this into the slow cooker to thicken the sauce into a rich, glossy gravy.
Sprinkle the shredded Gruyère or provolone cheese along with the mozzarella evenly over the top of the meatballs. Cover and increase the heat to HIGH, cooking for another 10 to 15 minutes until the cheese is fully melted and beautifully gooey.
Garnish with freshly chopped parsley or thyme before serving. These meatballs pair wonderfully with creamy mashed potatoes, buttered egg noodles, or toasted French bread to soak up the delicious onion gravy.

Variations

Use ground turkey meatballs instead of beef for a lighter option that still complements the rich onion sauce.
Replace Gruyère with Swiss cheese for a slightly milder, nuttier flavor profile.
Add a splash of dry white wine to the broth mixture for a subtle acidity that brightens the sauce.
Include sautéed mushrooms with the onions to introduce an earthy depth to the dish.
Top with fresh thyme sprigs instead of parsley for a more pronounced herbal aroma.
For a spicy kick, stir in crushed red pepper flakes to the broth before slow cooking.

Tips

Caramelizing the onions slowly is key: resist the urge to turn up the heat, as low and slow brings out the best sweetness and flavor.
Store leftovers in an airtight container in the refrigerator for up to 3 days; reheat gently in a covered skillet or microwave to preserve moisture.
This dish can be frozen for up to 2 months; thaw overnight in the refrigerator before reheating thoroughly.
When thickening the sauce, mix cornstarch with cold water before adding it to avoid lumps and ensure a smooth gravy.
Allow some headspace in the slow cooker to prevent overflow when stirring or as the sauce thickens.
For extra cheesy topping, broil the meatballs for 2 to 3 minutes after slow cooking to get a golden bubbly crust on the cheese.
Use low-sodium beef broth to control salt levels, especially since the French onion soup mix can be salty.