The night before or at least 4 hours prior, soak glutinous rice in water by dividing it equally (200 grams) in two separate bowls. This is important, if you do not do this the rice will not be soft and sticky after steaming.
On the day of cooking, strain the water from each bowl of soaked rice. To each bowl add coconut milk, water, salt and mix.
Grease a 9x9 square dish or pan.
To one of the bowls, add blue butterfly pea powder and mix well. You should have one bowl with white rice.
Pour the blue rice and the liquids onto a wide shallow pot or wide bowl. Place knotted pandan leaves into the rice. Cover and steam over medium heat for 25 minutes. Remove and keep warm. Repeat the same steps for the white rice.
Meanwhile, blend 10 pandan leaves in 200 ml of water. Pour the content into a sieve and strain the liquids, discarding the pulp. Pour this pandan extract into a medium size pot.
To the same pot, add custard ingredients: cornstarch, all purpose flour, eggs, coconut milk, and sugar. Mix well and place over stove top to heat over low medium heat as you continually stir it until it thickens (about 10-15 minutes). Do not bring to a boil and then reduce the heat. When you stir and chunks begin to form, remove off heat.
Stir the mixture well until the chunks have dissolved. Cover to keep warm.
Once your white rice has finished steaming, remove pandan leaves and remove from steamer.
Using a heat proof glove, slide the blue rice into your well-greased square dish to create 1 even single layer. Then use a spatula to pack the rice down very well. It must be packed well or the custard will seep through the cracks, affecting the layers. Smooth out the layer of rice.
Next slide the white rice over the blue rice and pack down very well. Smooth it out with spatula.
Then pour the pandan custard over top. Gently tap the pan on a surface to remove any air bubbles. Steam over medium heat for 30 minutes covered using a lid covered in aluminum foil or a clean tea towel.
Remove cake from steamer and allow to cool completely. Slice and serve.