Color the glutinous rice flour using natural dyes from butterfly pea flowers, beets, pandan leaves, and turmeric. You can buy pre-colored flour or color it yourself; combo packs are now conveniently available. Toast the sesame seeds until fragrant. Soak the mung beans until soft, then cook them with sugar until thickened.

For bánh chay: Use twice as much dough as for bánh trôi, place a cooled mung bean filling in the center, and roll into a ball. Gently press your thumb in the center to flatten slightly and create a small indentation.

Bring a pot of water to a boil. Drop the shaped balls into the boiling water. When they float to the surface, remove them and place them in a bowl of ice water. Then transfer to a plate.

For bánh trôi: Dip your finger in water, touch the sesame seeds, and gently press onto each rice ball so the seeds stick. For bánh chay: Mix granulated sugar with water to taste and bring to a boil. Stir in tapioca starch to thicken. Let cool, then pour the syrup over the bánh chay and sprinkle with sesame seeds, mung beans, or shredded coconut.