Prepare the meatball mixture: In a large bowl, combine the ground beef, finely diced yellow onion, breadcrumbs, minced garlic, egg, ketchup, mustard, Worcestershire sauce, salt, pepper, and chopped parsley. Mix until just combined.

Form the meatballs: Shape the meat mixture into 1 ½-inch balls. You should get about 18-20 meatballs.

Cook the meatballs: Heat the olive oil in a large skillet over medium heat. Cook each side for 6-7 minutes or until browned and fully cooked through. Remove the meatballs from the pan and set aside on a plate lined with paper towels to drain any excess oil.

Cook the onions: In the same skillet, melt the butter over medium heat. Add the sliced onions and cook until they soften and start to caramelize, about 5-7 minutes.

Add the broth: Pour in the chicken broth, beef broth, and add the beef bouillon cube. Stir until the bouillon dissolves.

Season the gravy: Stir in the onion powder, garlic powder, Worcestershire sauce, and Kitchen Bouquet (if using) to enhance the color and flavor.

Thicken the gravy: In a small bowl, whisk together ¼ cup cold water and 3 tablespoons cornstarch to create a slurry. Gradually stir the slurry into the gravy, letting it simmer and thicken for 3-4 minutes, stirring constantly to prevent lumps.

Combine: Add the cooked meatballs back into the skillet with the gravy, gently coating the meatballs in the sauce.