Put on the gloves, preferably gardening gloves that are thick enough to avoid being pricked. Make a tiny incision with the knife down the center of the sweet chestnut, running vertically from the top of the spiky case to the bottom.
Pry the spiky casing off the chestnut. The incision will rip, exposing the hard, mahogany-colored chestnut beneath it.
Hold the chestnut between your thumb and forefinger. Make an "X"-shaped incision on the bottom of the nut near the puckered stem scar. Make this incision about 1/16 inch deep.
Spread the incised chestnuts over the surface of the baking sheet. Put the sheet in the oven at 450 degrees Fahrenheit. Roast them for 20 to 30 minutes. Allow the chestnuts to cool to room temperature.
Crack them like any ordinary nut with a nutcracker by placing the nut between the pincers of the cracker and squeezing. Alternatively, you can use a ball peen hammer.