Combine water chestnut flour with 300ml of water. Whisk until flour is completely incorporated with the water. See note 1.
In a small pot, bring 300ml of water to a boil with the brown candy slabs. Whisk until the sugar is fully dissolved.
In the meantime, grease a loaf pan with a few drops of oil.
Once sugar is dissolved, turn the fire to low immediately.
Add water chestnuts into the pot, followed by the flour mixture. Continuously stir over low heat until mixture slightly thickens, then transfer it into the greased loaf pan.
Level the mixture with a knife or spoon, then steam for 30 minutes or until an inserted toothpick comes out clean.
Remove loaf pan from steamer then allow to cool. Run a knife along the edges of the pan then flip cake onto a cutting board. Slice then serve immediately. Enjoy! (See note 2)