The potatoes are washed and peeled, cut in half, covered with cold water and placed on top. A pinch of salt in the water. When they have cooked for 20 minutes and are done, the water is poured off and the potatoes are made into a pulp.
With a whisk or something similar, stir in the hot milk, then beat the puree until frothy and add the butter.
In the meantime, the apple has also been peeled, boiled and mashed. Mix both and season with salt, sugar and nutmeg.