Roasting chestnuts is very easy. Pierce each shell with a skewer, or slit it with a knife. Throw away any that have a hole in the side. Some other diner got there first! Put all the nuts into a heatproof dish such as a large bread tin or a roasting pan. Add one medium-sized chestnut which is whole (not slit). This one will explode noisily in the oven or the fire and tells you that the chestnuts are ready to eat. You might prefer to put a lid on the dish to save the inside of your oven from being splattered. If you prefer to avoid explosions altogether, you can take a little longer to prepare the chestnuts. Instead of just pricking them, or slitting them, carefully cut into the top of the chestnut twice in an X shape. It's best to give them plenty of room as a single layer on a tray; don't just pile them on top of one another.
The temperature you need for roasting chestnuts isn't too critical around 350 - 400 degrees is good. They usually take around twenty minutes or more to cook, depending upon the size. We usually just put the oven on full. In an open fire put them in a sealed fireproof dish, or wrap them in tinfoil and put them at the side, in the embers.
If they look greyish when cooked they have probably gone off. They should mainly be a warm buttery yellow or creamy beige colour. However, there are usually some greyish tones, so don't be too easily put off!
The easiest way to eat them is to use a knife to cut them open and a teaspoon to scoop out the flesh. If there are any left over afterwards, it's best to throw them out; they seem to lose their subtle floury texture if they are re-heated.
You can also boil chestnuts to cook them before adding to a recipe. Boil them for about fifteen to twenty minutes in enough water to cover them. If you want to steam them slice them in two first.
Once you have boiled chestnuts, it is easy to slice them open and scoop out the flesh with a teaspoon. Store the cooked chestnuts in the fridge until you want them. You can fry them in a little oil with onions or anything you like. They are just as delicious as roasted chestnuts and really rather more versatile.