Make batter: Combine flour, baking powder, and salt in a large bowl. Drizzle in sesame oil. Gradually add water, whisking constantly until smooth; batter should be the consistency of cream. Let sit for at least 30 minutes.

Fill a deep pan or wok with oil and slowly heat to 375 degrees F (190 degrees C).

Prepare chicken: Mix together cornstarch and white pepper in a large shallow dish. Dust chicken in cornstarch mixture, then dip into batter, evenly coating each piece.

Working in batches, fry coated chicken in hot oil until golden and no longer pink in the center, 4 to 5 minutes. An instant-read thermometer inserted into the center should read at least 165 degrees F (74 degrees C). Use a slotted spoon to remove fried chicken to a clean kitchen towel to drain.