Prepare the Mung Bean Filling: Rinse mung beans thoroughly, soak overnight or in hot water for 2 hours, cook until tender, then mash with sugar, salt, and optional vanilla until smooth.

Make the Outer Shell Dough: Combine half of warm water with sugar and salt until dissolved. Gradually mix in remaining ingredients to form a slightly dry dough. Rest for at least 2 hours, up to 8 hours.

Form the Bánh Cam: Take a small portion of dough, flatten, place a ball of mung bean filling in the center, wrap dough around the filling, shape into a ball, and roll in sesame seeds.

Frying: Heat oil to 285°F, deep fry sesame balls for about 11 minutes until golden brown, turning occasionally. Avoid overcrowding.