Peel and chop the potatoes. Bring to the boil in a pan of salted water. Cook for about 20 minutes or until tender.
Drain and dry well. Mash the potatoes with a potato masher.
Heat the milk with the butter (optional; you can add the butter as is). Pour it slowly over the potatoes. Don't use it all at once. You may need more or less. Depending on the result you want.
Season to taste with salt, pepper and nutmeg.
Smooth mashed potatoes
Peel and chop the potatoes into equal pieces. Bring to the boil in a pan of salted water. Cook for about 20 minutes or until tender.
Drain and dry well. Use a potato ricer to mash the potatoes. Don't have one? You can also press the potatoes through a coarse sieve or colander. Try not to rub the mix too much, but really push the potatoes through.
Cut the butter into cubes and add to the mashed potatoes with the warm (not boiling!) milk. Keep mixing until you get the right consistency.