1 Cook the potatoes in salted, boiling water for about 25 minutes. Blanch the carrots in boiling, salted water for about 6 minutes. Drain well.
2 Heat 2 tbsp butter and brown the mince, breaking it up to brown right through. Stir in the onion and fry briefly. Then stir in the stock and tomato puree, add the diced carrots and thawed peas and cook for a further 3 minutes or so. Turn into a greased baking dish.
3 Drain the potatoes, add 2 tbsp butter and the milk and season with salt, pepper and nutmeg. Mash coarsely with a potato masher and check the seasoning.
4 Spread the mashed potato on top of the mince, scatter with coarsely grated cheese and bake in a preheated oven (200°C | 400F | gas 6) until the cheese begins to melt.