Rinse chestnuts. Cut a cross on the flat side of all nuts. Preheat oven to 450 degrees. Place chestnuts on a cookie sheet and bake for 15 minutes to ½ hour, depending on size and degree of tenderness desired. Roast longer if you wish them to be more tender. Keep checking the chestnuts every 5 to 10 minutes. The area where you made a cross should be bending upwards. Open several and test for softness. Peel when cool enough to handle and enjoy eating.