Rinse the glutinous rice until the water runs clear. Add the alum and enough water to cover the rice. Stir to combine and soak overnight.

Drain and rinse the soaked rice thoroughly to remove the alum. Let it drain for a few minutes.

Transfer the rice to a steamer basket. Add the pandan leaves. Place the basket over boiling water and steam for about 20 minutes, or until the rice is cooked through.

In a mixing bowl, combine the coconut cream, sugar, and salt. Stir until dissolved. Add the steamed rice and mix well. Let it sit for 30 minutes so the rice absorbs the coconut mixture. Serve with ripe Nam Dok Mai mango, extra coconut cream (optional), and roasted split mung beans.