2. To roast the chestnuts in the oven: Lay the nuts in a single layer on an ungreased baking sheet, and roast in a 350°F oven until the nuts are fragrant and the scored portions begin to separate from the shells, 15 to 20 minutes. (If you're going to eat the chestnuts plain, increase the heat to 400°F and bake until the shells give slightly when pressed with oven mitt-protected fingers.)
3. To roast the chestnuts in a chestnut pan: Heat the pan over medium-low heat and add the chestnuts. Cook, tossing the chestnuts frequently, until the shells crack and the chestnuts are cooked through, 30 to 35 minutes over a gas flame burner, 35 to 40 minutes over an electric or conduction burner.
4. Transfer the nuts to a platter or heatproof surface and cover with a damp kitchen towel to keep them warm.
5. Using a kitchen towel or pot holder, pick up each nut and, with your fingers or the knife, peel back the scored X. Peel off the hard outer shell and the thin, beige, soft inner skin. Discard any nuts that, once peeled, look dried out.
6. Eat the chestnuts immediately or use as directed in a recipe.