Because of the size of the chestnuts and the difference in temperature of each oven, the roasting time provided in the recipe is for reference only. When you are almost done roasting, remove a chestnut and taste it to see if it is cooked through, and if not, extend the roasting time a bit. The chestnuts must be fully roasted for them to be delicious.

Using a knife to make slits in the chestnuts will allow them to crack smoothly while roasting. If you're lazy and skip this step, be prepared for a loud popping sound in the oven when the chestnuts are roasting, and not all chestnuts will crack.