Cover the potatoes with cold water in a pan and add a pinch of salt.
Cover the potatoes with cold water in a pan and add a pinch of salt. Bring to the boil, then simmer for 15-20 minutes or until completely tender when pierced with the tip of a sharp knife.
Drain in a colander and peel the potatoes while they are still hot.
Meanwhile, heat the olive oil in a pan. Add the onion, celery, carrot and garlic and sauté for 3-4 minutes until just beginning to soften but not colour.
Stir the mince into the pan and cook for 2-3 minutes until browned, breaking up any lumps with the back of a wooden spoon.
Stir in the tomato puree and red wine/stock and cook gently for another 10 minutes until completely tender. Season to taste and keep warm or reheat as needed.
Transfer the beef to an ovenproof casserole dish.
Push the cooked peeled potatoes through a potato ricer or sieve using a spatula. Quickly heat the milk in a pan. Beat the butter into the warm mashed potato and then add enough milk to make a smooth puree. Season to taste.
Preheat the oven to 190C/375F/Gas Mark 5. Pipe or spoon the potatoes onto the top of the meat mixture. Sprinkle with approximately 50g grated cheese and bake in the oven for approximately 12-15 minutes or until the potato topping has become golden brown and the meat mixture is really hot on the underneath.