Pour oil 3 inches deep into a 4-quart saucepan. Place the pot over medium heat and bring the oil to 300°F. While the oil is heating, combine the flour, coconut milk, ¼ cup water, and the egg yolk in a medium bowl.

In a separate bowl, whisk the egg white or beat it in an electric mixer until it forms stiff peaks. Using a flexible spatula, fold the white into the chestnut batter, then set the bowl aside.

Constantly monitor the oil temperature to make sure that it stays at 300°F. To fry, drop 1 teaspoon at a time into the oil using a heat-resistant plastic spoon. Fry for 30 seconds, then flip over and fry for 20 seconds, until golden brown. Work carefully to avoid getting burned. Remove from the pot with a slotted spoon and place on a paper-towel-lined plate.

These can be tossed in sugar or served plain and enjoyed immediately or at room temperature.