Method

1 Heat the oil in a large non-stick frying pan on medium. Add the onion, celery, carrot and zucchini. Cook, stirring occasionally, for 6-7 minutes or until the vegetables soften slightly. Increase heat to high. Add beef mince. Cook, breaking up the mince with a spoon, for 3-4 minutes or until browned. Preheat oven to 190°C (fan-forced).
2 Put the gravy powder, water, tomato purée and Worcestershire Sauce in a small bowl. Whisk to combine. Add to the frying pan. Cook, stirring, over medium heat until the sauce comes to a simmer. Simmer, stirring occasionally, for 10 minutes. Add the peas and thyme leaves. Cook for 2 minutes.
3 Meanwhile, cook potato, partially covered, in a large saucepan of boiling water for 10-15 minutes or until tender. Drain well. Mash until smooth.
4 Spoon the mince mixture into a 2.25L (9-cup) ovenproof dish. Spoon the mash over. Using a fork, rough up to form peaks. Sprinkle the cheese over.
5 Put the dish on a baking tray. Bake for 25-30 minutes until cheese melts and the potato is golden brown.
6 Divide between plates to serve.