Add water to the dry glutinous rice until the water is about 1 1/2 inches above the rice.

Rinse the glutinous rice 4 times, or until the water runs clear. Then add clean water until it covers the rice by 2–3 inches. Soak for 3 hours.

After soaking, drain the rice thoroughly using a strainer. Steam the rice for 20 minutes.

Prepare the coconut milk mixture for the sticky rice: Pour the thick coconut milk into a large mixing bowl. Add salt and granulated sugar. Stir to combine, then knead with pandan leaves until fragrant and the sugar and salt are fully dissolved. Strain through a fine sieve or cheesecloth.

When the rice is fully cooked, immediately transfer the hot rice into the coconut milk mixture. Use a spatula to mix so the coconut milk is absorbed into the rice. Cover tightly and let sit for 10 minutes. Uncover and stir again with a spatula, then cover and let sit for another 20 minutes. Stir once more, cover, and let sit for another 10 minutes. The sticky rice should now be glossy and ready to serve.

Prepare the ripe mangoes by peeling and slicing them onto a plate. Serve with a portion of sticky rice on the side and drizzle with coconut milk.