Preheat oven to 425. Score the chestnuts with an X on the rounded side of the chestnut. Heat a pan of water to boiling and soak the chestnuts for 1–2 minutes. This will help them steam as they are roasting.
Drain the chestnuts and set aside the pan. Lay out a piece of foil on the counter. Place the chestnuts, rosemary, butter, salt and nutmeg on the foil. Use your hands to toss the ingredients together. Gather up the sides of the foil and place in the empty pan, leaving the chestnuts in a single layer.
Put the pan in the oven and roast the chestnuts for 35–40 minutes, until the edges of the shells are beginning to turn up.
Place in a bowl and pour all butter and spices over the top. Check the seasonings and add more salt if desired. Serve hot.
Adapted from Bon Appetit Photo by Bradley W. Bergey.