If using bunga telang, rinse flowers gently. Drain. Blot gently with paper towels. Pound finely. Strain to yield 2-3 tsp juice. Set aside. Discard pulp.

Put pandan water back in the pot. Add sugar and salt. Stir over low heat till salt and sugar dissolve. Turn off heat. Add coconut milk. Stir till evenly mixed. Add tapioca starch. Mix thoroughly. Strain into a mixing bowl. Push undissolved starch through strainer.

Bring kettle to the boil and set aside.

Rinse 15-cm square cake tin to make it wet. Line bottom with parchment paper.

Bring steamer to a rolling boil. Pour enough white batter into cake pan to form a layer 3 mm thick, about 100 ml. Place pan in steamer. Steam 5 minutes over rapidly boiling water. Steam another layer of white, then blue. Repeat the white-white-blue sequence twice, making 9 layers in total.

Each layer needs about 90 ml batter, other than the first one. Stir batter to mix starch evenly before measuring each round of batter. Have measured batter ready before lifting lid on steamer. Once lid is removed, quickly pour batter into cake tin and cover steamer. Every layer is steamed 5 minutes except the topmost, which gets 10 minutes.

Make sure steamer doesn't boil dry. To top up steamer: a) wait till previous layer of batter is cooked; b) reboil water in kettle; c) add boiling water to steamer as necessary; d) bring steamer back to a rolling boil, covered. After step 4, proceed to steam more layers as described above.

When all 9 layers are done, remove kueh lapis to a wire rack to cool down completely and set, about 3 hours.