Peel the potatoes, cut into quarters and boil in salted water until soft. Strain, let steam out (possibly in a slightly preheated oven).
Mash with a potato masher, press through a potato press or strain through a sieve. Add the butter and let it melt, stir in.
Heat the milk, gradually folding it in to make a thick, smooth paste. Season with salt and grated nutmeg.
For the roasted onion, peel the onion, cut into slices. Heat the oil in a coated pan, roast the rings in it and place them on top of the mashed potatoes.
Preparation Tip:
If you increase the amount of butter, your figure will not thank you, but your taste buds will. You can also refine mashed potatoes well with a dollop of whipped cream, and some add a touch of truffle oil.