Soak the peeled split mung beans (mung dal) in water for at least 2 hours until softened. Drain and cook by either steaming or boiling until fully tender. Blend the cooked mung beans with sugar, vegetable oil, and a pinch of salt until smooth. If the mixture is too soft to hold its shape, transfer it to a pan and cook over low heat, stirring continuously, to evaporate excess moisture. Continue cooking until the mung bean paste becomes a soft, pliable dough-like consistency that can be shaped into balls.

If you are using sweet potato or potato, steam or boil it until fully cooked, then mash it until smooth.

Gradually pour boiling water into the flour mixture (including mashed sweet potato/potato, glutinous rice flour, rice flour, cornstarch, sugar, and salt), a little at a time. After adding a small amount of boiling water, knead the dough with your hands until incorporated. Repeat this process several times until the dough comes together into a smooth, pliable ball.

If you have a plastic or silicone sphere mold, you can use it to portion the filling evenly. If not, you can divide the filling into 15-20 small portions and roll them into evenly sized balls. Similarly, with the dough, divide it into 15-20 equal portions. Cover both the filling and the dough balls with plastic wrap to prevent them from drying out.

To assemble, take one piece of dough and flatten it into a thin disc, then place a filling ball in the center. Carefully wrap the dough around the filling, ensuring that it is completely sealed.

For the sesame coating, pour white sesame seeds onto a plate and roll each assembled ball over the seeds until evenly coated. If the dough surface is too dry for the sesame to stick, brush a little water on the dough before rolling.

Heat a sufficient amount of oil in a deep pan, then carefully add the sesame balls to fry until golden. Fry over medium heat to allow the dough to cook evenly, giving the outer shell time to turn golden and puff up. Once done, remove the sesame balls from the oil and drain them using a paper towel or a mesh strainer to absorb excess oil, making them less greasy and more enjoyable.

Bánh cam/bánh rán are best enjoyed while still warm for the crispiest texture.