Preheat the oven to 200oC, gas mark 6. Boil the potatoes for 10-12 minutes until tender. Drain and return to the pan. Add the milk and mash well, season to taste.
Meanwhile, fry the mince and onion in a large saucepan for 5 minutes. Add the gravy granules, 200ml boiling water, Worcestershire sauce and vegetables and bring to the boil. Transfer to an ovenproof dish or 4 individual dishes. Top with the mash and bake for 30 minutes.