Toast both black and white sesame seeds in dry pan over medium heat for 6-7 minutes, until fragrant. Set aside to cool completely.
Combine cooled sesame seeds and icing sugar, mix well. Process in 2 batches into fine sesame powder.
Combine plain flour and cornstarch, sift through. Add in salt, mix well. Add in sesame powder, mix until combined. Add in vegetable oil gradually, mix into a dough. (Reminder: The water absorption capacity for different brand of flour is different. If your dough is drier, add in more oil; If your dough is wetter, add in more flour, until it reaches the consistency as shown in the video.)
Take out ½ tbsp of dough (about 8-9 g, use ½-tbsp measuring spoon), press until firm and shape gently into a ball. Top with white sesame seeds. Arrange on lined baking tray.
Bake in the preheated oven at 170°C/340°F for 20 minutes. (Reminder: The baking temperature and time are just for reference, adjust according if necessary.)
Set aside to cool completely.
Video
Notes
This recipe yields 120 pieces.The nutritional value for reference is for 1 piece.