Start by scoring chestnuts: Place the flat side of the chestnut down on a cutting board. The rounded side, (aka the belly side) should be facing up. Hold the chestnut firmly and cut horizontally across the rounded side using a sharp paring knife or a chestnut knife, if you have. Then turn the chestnut 90 degrees and make a second cut forming an X. As you are cutting, do your best not to score the inner skin. Continue with the rest of the chestnuts.
Place scored chestnuts in a bowl, cover them with cold tap water and let them soak for an hour.
Prepare the charcoal grill or open fire pit. When the briquettes are ready, distribute them evenly to create a flat bed that the cast iron skillet can rest on. If you have a grill grate, place it on top. Carefully place the cast iron skillet on the hot coals (or grate) and let it warm for 5-10 minutes.
Add scored chestnuts to the cast iron skillet in a single later. If they don’t fit in one layer, you may have to do this in two batches.
Depending on the type of chestnuts you are using, they should open up as soon as they hit the pan.
Let them cook, stirring occasionally, for about 10-12 minutes*. There might be some smoke coming out and that is normal. You will know that they are cooked once the outer skin is fully opened up exposing the inner yellow nut. However, the best way to check doneness is to peel one and give it a taste. If it is soft and creamy it should be done.
If it is not fully roasted at the end 10-12 minutes, you can put a lid on it for a few minutes to trap the air inside. However, I highly recommend keeping a close eye on it and checking every few minutes.
When they are fully roasted and opened up nicely, let them cool for a few minutes and peel them right away.
If they are difficult to peel then let them steam for a few minutes. To do so, carefully remove the cast iron skillet from the grill and transfer the roasted chestnuts onto a tea towel. Collect the edges of the towel in the middle and turn it into a small pouch. Let them steam in the “pouch” for 5-10 minutes. Alternatively, you can use a paper bag. Simply place the hot roasted chestnuts in it, roll the bag trapping the steam inside and let it rest for 5-10 minutes.
Transfer the roasted chestnuts onto a platter and remove the outer shell of the chestnuts when they are still hot by gently pulling back on the scored “X”, peeling away the papery skin and exposing the yellow flesh inside. If you are unable to remove the fuzzy inner skin by hand, use a small sharp knife to peel it, being careful not to pierce the yellow nut inside. Discard the bad chestnuts that are spoiled inside.
Enjoy roasted chestnuts on their own or use it with your favorite herbs or seasoning.