This potato purée is a refined, incredibly luxurious version of good old-fashioned mashed potatoes—and that means Chef Emma Bengtsson doesn't stint when it comes to butter and milk! We recommend using a food mill or potato ricer to get extra silky-smooth results.
Add cubed potatoes to a medium saucepan with a big pinch of salt and enough cold water to cover. Bring to a simmer over medium-low heat and cook until very soft and almost falling apart, about 20 minutes. When potatoes are cooked, drain well. Then place them back into the hot pot (with the heat turned off) to evaporate any residual moisture, 30 seconds.
Run potatoes through a food mill or potato ricer into a mixing bowl. Add butter and stir well to combine; then pour in the warm milk and whisk until thoroughly combined. Add salt to taste and place back into the saucepan. Over very low heat, whisk again to release extra moisture in the potatoes.
When potatoes are smooth and creamy, but still hold their shape when folded over, transfer to serving dish. Sprinkle with chopped parsley and serve immediately.
Potato purée can be made a day ahead and stored in a covered container in the refrigerator. To reheat, add to pot with a splash of milk and stir over low heat until hot.