Place the whole potatoes in a steamer basket set over a saucepan of boiling water. Steam for 20–30 minutes, depending on the size of the potatoes. Check the water from time to time to make sure it doesn’t dry out during cooking. Set the potatoes aside to cool a little, then peel them when they are cool enough to handle.
Coarsely mash the potatoes while they are still warm. Pour in the r