Peel the potatoes and cut them into even-sized pieces, about 3×3cm (if they aren’t even they won’t cook at the same speed).
If you choose to boil the potatoes, make sure you only cook them until tender and not so they start getting ragged around the edges or they’ll become water-logged. Then drain and briefly steam dry in the pan.
Once you have nice, dry, cooked potatoes add milk or cream, if using, and put the pan back over the heat until the liquid is also hot.
Add a good knob of butter then mash quickly (or go in with your electric whisk), until smooth. Season, with nutmeg too if you like.