Slice half of the water chestnuts into small pieces, and smash the other half. Put aside for later use.
Dissolve the water chestnut flour with 650mL water. Add the water gradually, and keep stirring until everything dissolves.
Sieve the water chestnut mix two times, try to dissolve the residue at the bottom as much as possible.
In a small pot, add the rock sugar and Chinese slab sugar. Pour 650mL of water. Heat it up and melt the sugar. Stir and mix well.
Add 2 ladles of the water chestnut mix to the sugar mix. Remember to mix the water chestnut mix before using it each time. Keep mixing. Add another 2 ladles and keep mixing.
Remove the small pot from heat and pour the whole mix to the water chestnut mix. Keep mixing until no big lumps.
Pour the mix back to a pot. Add the water chestnuts, heat it up with low heat. Keep stirring and mixing for 5 mins.
Brush some oil on the container which you plan to use for steaming. Pour the mixture into it. Spread it out evenly.
I use a wok to steam my food. So put some water in the wok, leave it on high heat. When the water is boiling, put the water chestnut cake in. Steam for 30-35mins.
Once it's done, leave it to cool down completely.
Either enjoy it like that or pan-fry it as you like!