adapted by http://theresalwaysthyme.blogspot.com/
Choose chestnuts that are smooth, shiny and heavy. Soft ones are rotten. Always score your chestnuts before cooking. Roasting time can vary depending on the chestnuts. Chestnuts are harder to peel once they have cooled completely. Boiling the chestnuts before roasting, softens the shells, and the chestnuts roast in only 12-18 minutes. If you're boiling them first, make the x's in your chestnuts before you boil them.
Be really careful when you score them!
Preheat the oven to 350 degrees F.
Use a sharp paring knife or a serrated knife to cut an X into one side of each chestnut, be really careful doing this. They can be slippery. Boil the chestnuts in water for about 10 -15 minutes (optional, but I always do it this way to soften them, you can omit this part and just roast them after scoring them but they don't get as soft!)
Arrange chestnuts on a baking sheet or in a shallow pan, with the cut sides up. Roast in oven for 15 to 25 minutes, or until chestnuts are tender and easy to peel. Peel the nuts when they are cool enough to handle, and eat.