Spray a large lidded saucepan with low-calorie cooking spray and cook on a high heat until hot. Add the minced beef, celery and leek and fry for 5 minutes. If you’re using Quorn instead, you can add this in the next step.

Add the sweetcorn, passata, yeast extract/marmite, Quorn mince (if using) and 300ml of boiling water then bring to the boil.

Cover and simmer for 10 minutes. If using beef mince, ensure it is cooked by the end of this period. If it still has pink bits, fry for a little longer until thoroughly cooked.

Meanwhile, bring a large pan of water to the boil, add the potatoes and simmer for 15 minutes until tender.

Drain, reserving around 2 tbsp of the cooking liquid, and mash, adding the reserved cooking liquid to make it nice and smooth.

Preheat the grill to medium heat and pour the mince mixture into a large dish. Add the mashed potato topping and grill until golden which should be around 5-10 minutes.