Preheat your oven to 180°C (350°F).
In a large mixing bowl, combine the ground beef, onion, celery, carrot, green onions, garlic, Worcestershire sauce, egg,⅓ cup of the ketchup, breadcrumbs, parsley, salt, and black pepper.
1 ½ pounds ground beef, ½ cup onion, 1 rib celery, ½ cup carrot, ¼ cup green onion, 3 cloves garlic, 2 teaspoons Worcestershire sauce, 1 large egg, ⅔ cup ketchup, ½ cup fresh bread crumbs, 3 tablespoons fresh parsley, Salt and pepper
Using your hands or a sturdy spoon, mix the ingredients together until well combined.
Transfer the meat mixture into a 5-by-9-inch loaf pan and press it down evenly.
In a small bowl, mix the remaining ketchup (about 2-3 tablespoons), Worcestershire sauce, mustard, and sugar until well combined. Brush or spread the ketchup mixture over the top of the meatloaf.
1 tablespoon Dijon mustard, 1 tablespoon Worcestershire sauce, 2 tablespoons light-brown sugar
Bake the meatloaf in the preheated oven for 45 minutes.
After 35 minutes of baking, remove the meatloaf from the oven and brush or spread any remaining ketchup mixture over the top. Return the meatloaf to the oven and bake for the remaining 10 minutes.
Remove the meatloaf from the oven and let it cool slightly for 5-10 minutes before slicing and serving.