Heat the over to 425 degrees.

Place the chestnuts, flat side down, on a cutting board.
With a serrated knife, slice into each chestnut. Be sure to cut through the entire shell.

Add the chestnuts to a pot of cold water.
Once the water boils, remove the chestnuts with a slotted spoon.

Arrange the chestnuts on a cookie sheet, flat side down.

Place the cookie sheet in the oven and bake for about 20-25 minutes.
Shake the baking pan occasionally.

When the nuts are fully cooked, shell them and store any extras in the refrigerator.

Note: Test one chestnut to determine if the batch is fully cooked.