Cover chestnuts with water in a large saucepan.

Bring to a boil and simmer for 8 minutes.

Drain the water and discard.

Rub off the brown inner skins using a kitchen towel.

In a large saucepan, combine sugar, water, and vanilla essence.

Cook over low heat until the sugar dissolves.

Increase heat and simmer for 10 minutes to create a syrup.

Pour the syrup and chestnuts into a large bowl.

Let the chestnuts stand in the syrup for 12 hours.

Return the mixture to the pan and boil for 1 minute.

Return the mixture to the bowl.

Let the chestnuts stand for 24 hours.

Repeat the boiling and resting process 3 times until the syrup is absorbed.

Preheat oven to 65°C (150°F).

Cover a wire rack with greaseproof paper.

Place the chestnuts on the wire rack.

Place in oven with oven door open for 2 hours or until hardened.

Remove from oven and let cool.

Store in a container lined with greaseproof paper.