Peel and slice the mangoes.
In a bowl, mix glutinous rice flour, cornstarch, white sugar, and milk to create the mochi batter. Mix it until it's smooth like yogurt.
Then, cover it with plastic wrap and poke the plastic wrap to make tiny holes.
Steam for 30 minutes. The dough should become semi-solid after steaming.
After steaming, add corn oil and distribute it evenly in the dough. Remember to wear kitchen gloves.
Keep mixing the dough by twisting and pulling it up with your hands.
Take a piece of the dough and flatten it into a circular wrapper.
Place a slice of mango in the center of the wrapper.
Pinch the edges to seal it, and shape it nicely into an oval mochi.
Sprinkle coconut powder on a plate and gently coat the mochi with a layer of coconut powder.