Wash and peel the potatoes.
Cut them into similar-sized chunks (about 2-3 cm or 1.5 inch cubes).
Place the chunks in a medium-sized pot and top with cold water.
Bring to a boil, then let the potatoes simmer for 15-17 minutes, until they are soft (test with the tip of a sharp knife).
Drain the potatoes and add the chunks to a large bowl.
Mash them with a potato ricer (or masher) bit by bit, and return the mashed potatoes to the warm pot.
Place the pot on medium-low heat.
Add the butter and mix well until melted.
Top with the milk a bit at a time, allowing the potatoes to soak up the liquid.
Season to taste and serve.