Rinse the glutinous rice thoroughly in water three times. For the fourth rinse, add a small piece of alum and soak the rice for 10 minutes. Remove the alum, then soak the rice in the alum water for 5 hours.

After 5 hours, rinse the rice again until clean. Steam the rice over boiling water for 20 minutes.

While the rice is cooking, combine 1 cup coconut cream, sugar, salt, and pandan leaves in a pot. Heat over medium heat on the stove, stirring constantly. Do not let the coconut cream boil. Once it is hot and steaming, turn off the heat and stop stirring.

When the rice is fully cooked, transfer it to a large mixing bowl. Pour all of the prepared coconut mixture over the rice. Stir in one direction until the rice and coconut cream are well combined. Cover and let sit for 15 minutes. Uncover, stir the rice again, then cover and let sit for another 30 minutes.

To make the coconut sauce: In a small pot, combine 1/3 cup coconut cream, salt, and rice flour. Stir until everything is dissolved. Cook over low heat, stirring constantly, until the sauce thickens. Remove from heat.

Soak the split mung beans in water for 30 minutes. Drain well, then fry until golden and crispy. Use as a topping for the mango sticky rice.