Preheat your oven to 200°C (390°F) top/bottom heat.
Halve the 1 kg starchy potatoes and place them cut-side up on a baking sheet lined with parchment paper.
Bake the potatoes for about 50 minutes in the preheated oven until they are soft.
Press the baked potatoes through a potato ricer. Optionally, you can remove the skin beforehand or take it out of the ricer after pressing.
Let the pressed potatoes steam out well, then place them, well covered, in a cool place overnight, for example, in the refrigerator.