With a sharp knife, make a cut on the bent part of each chestnut, side to side (be careful not to injure yourself). Make sure to cut the outer skin and also the inner skin, while trying not to damage the fruit too much.
Take a saucepan of water to a boil and dip a dozen chestnuts for a few minutes. Meanwhile, place a pan on the stove to warm.
When you see the chestnuts start to open, take them with a shimmer, quickly put them in the hot pan and cover with a lid. After less than a minute, the chestnut peel will open wide. Turn off the heat, pull them up and try not to burn your hands (at least not too much), scale them, be careful not to break them.
If the chestnuts are quite compact (like "maroon"), they will scale very easily. On the other hand, if they have many "creases", you will find some difficulty removing the inner skin. Be patient and help yourself with a toothpick to go through the "wrinkles".
Keep in mind that the pellicle is quite easy to remove until it is hot, so we have to cook a few chestnuts at a time. If they get cold and you can no longer peel them, dip them again in the boiling water (not the same as you put them with the peel, otherwise they will become dark) for a few seconds, pull them out and try again.
Repeat this operation with the other chestnuts until you have peeled them all.