6 medium potatoes, peeled and washed
Sea salt and freshly ground black pepper
50g/2oz unsalted butter
180ml-200ml/6fl oz-7fl oz buttermilk or crème fraîche
50g/2oz Parmesan cheese, freshly grated
Cut the potatoes into small, even-sized pieces and place in a saucepan containing enough cold water to cover them. Add one-and-a-half teaspoons of salt. Bring to the boil over a medium heat, then turn down the heat, put the lid on and simmer for 15 to 20 minutes until the potatoes are really tender. The water will become cloudy and the potatoes should literally crumble and fall apart when pierced with a fork. Drain the potatoes and set aside.
Add the butter and the buttermilk or crème fraîche to the pan in which the potatoes were cooked and place over a low heat until the butter is melted and the milk is almost simmering. Take off the heat.
Return the potatoes to the pan and mash thoroughly, using a hand-held potato masher, until really smooth. Add a little more buttermilk if the mash feels a little firm, but it must be warmed through before adding. Stir in the Parmesan and season with plenty of pepper.
Serve piping hot – this is a must. If not serving at once, you can reheat the mash carefully over a low heat, stirring to avoid it catching and burning on the bottom, which gives an unpleasant smoky flavour.