Rinse the glutinous rice in water until the water runs clear. If you have alum, gently rub the rice grains with it to make them more translucent and shiny. Soak the rice overnight.

The next morning, rinse the soaked rice 3 more times (gently). Steam the rice for 20 minutes, adding 3 pandan leaves to the steaming water.

Pour 1 1/4 cups (about 300 grams) of coconut milk into a pot. Add 1 1/2 teaspoons salt and 1/2 cup (about 100 grams) sugar. Heat over low heat, stirring until the sugar dissolves. Pour this mixture over the hot, freshly steamed rice. Gently mix the rice and coconut milk together (stir in one direction to avoid breaking the grains). Cover and let sit for 20 minutes, then set aside.

Press the sticky rice into a cake mold, packing it tightly to your desired thickness. Arrange sliced mangoes on top as shown in the picture. Add another layer of sticky rice on top (press gently but firmly), then arrange more mango slices as shown.

Once arranged, remove the cake from the mold. It should look beautiful and hold its shape.

To slice the mangoes, cut as close to the pit as possible to get large pieces, then slice thinly as shown. Arrange the slices into a flower shape for decoration.