2) Peel and slice potatoes and add them to the simmering water, together with a few pinches of salt. Increase the heat and bring to the boil. Cook for about 15 minutes until a skewer comfortably slides through the potatoes.
3) Drain the potatoes in a large colander and put them back into the saucepan. Add the milk, butter and nutmeg and mash the potatoes until smooth and creamy.
4) Stir in the Dijon mustard and add salt and pepper, to taste.