In two separate bowls, soak 7.05 oz or 200 grams glutinous rice in each bowl with enough water the night before or 4 hours prior (or the rice will not be soft and sticky after steaming). On the day of cooking, strain out the rice water with a fine sieve. Transfer the rice back into each bowl. Add instructed amounts of coconut milk, water, salt to each bowl and mix well.
To one of the bowls of rice, mix in blue butterfly pea powder until evenly colored, leaving the other bowl uncolored.
Next pour the blue rice and the liquids onto a large shallow bowl. Then place knotted pandan leaves into the rice. Fill a large wok or steamer pot halfway with water and place a wire rack or bamboo steamer inside. Bring to a boil on medium-high heat and then reduce to medium heat. Carefully place the plate of blue rice on top of the wire rack or bamboo steamer.
Cover and steam the blue rice for 25 minutes. Occasionally checking it to ensure there's enough water in the steamer and refill with hot water if needed. Remove the plate from steamer with oven mitts and remove the pandan leaves from the rice. Keep the rice warm.
Next transfer uncolored rice with the liquids to a wide shallow bowl. Transfer to the steamer. Cover and steam on medium heat for 25 minutes checking occasionally if the steaming water needs to be refilled with hot water. Once white rice is done steaming, remove pandan leaves and remove from steamer. Set aside and keep warm.
To make Pandan Custard Layer: add 10 pandan leaves and 200 ml or 6.76 fl oz of water into a blender and blend until smooth. Pour the content into a fine sieve and strain the liquids, discarding the pulp. Pour this pandan extract into a medium sized pot. Then whisk in the remaining pandan custard ingredients: cornstarch, all purpose flour, eggs, coconut milk, and sugar. Heat the pot on the stove over low-medium heat continually stirring until it thickens. Do not bring to a boil.
When chunks begin to form as you stir, remove the pot off heat. Next stir the mixture well until the chunks have dissolved completely. Cover to keep warm.
Then grease a 9x9 square baking pan or baking dish with vegetable oil. Using oven oven mitts, slide the blue rice into the greased square baking pan to create an even layer. Use a spatula to pack the rice down hard ensuring there are no holes or cracks to prevent the custard layer from seeping through them. Smooth out the layer of rice.
Then slide the white rice over the blue rice and pack down very well ensuring no cracks and holes. Smooth it out with spatula.
Then pour the pandan custard over top. Gently tap the baking pan on a even surface to remove any air bubbles. Transfer the baking pan back into the steamer ensuring there's enough water in the wok or steamer pot.
Steam over medium heat for 30 minutes covered using a lid covered in aluminum foil or a clean tea towel. This prevents the water droplets from making holes into your pandan custard layer.
Finally remove the baking pan from steamer with oven mitts and let the cake cool down inside the baking pan. Then slice the cake with a wet and oiled knife at an angle and serve to enjoy!