Slow Cooker Meatballs & Gravy

Bahan-bahan (4 porsi)

• 1 tablespoon butter
• 1 medium onion (sliced)
• 24 ounces frozen meatballs (or homemade meatballs below*)
• 10.5 ounces beef broth
• 10.5 ounces condensed French onion soup
• ½ cup heavy whipping cream
• 2 cloves garlic (minced)
• 1 tablespoon Worcestershire sauce
• 1 bay leaf
• salt and black pepper (to taste)
• 2 tablespoons cornstarch