Make Mung Bean Paste: Blend steamed mung beans with coconut milk, sugar, and salt until smooth. Mix in tapioca and rice flour. Set aside.
Prepare Pandan Layer: In a bowl, whisk together pandan juice, sugar, tapioca starch, rice flour, and coconut milk until smooth.
Set Up Steamer: Preheat your steamer. Lightly grease a heatproof tray or line with parchment.
Layer and Steam: Pour 1/4 cup of pandan layer into the tray and steam for 5 minutes. Then pour the same amount of mung bean mixture on top and steam for 5 minutes. Repeat alternating layers until all batter is used.
Final Steam & Cool: Once all layers are done, steam the full cake for an additional 20 minutes to set. Cool completely before slicing.