If using drumsticks, cut each into 2–3 pieces; trim any excess skin as desired.
Set the Instant Pot to Sauté and heat the oil until shimmering.
Working in batches if needed, sear the chicken pieces in the hot oil until lightly browned on all sides, using tongs to turn; remove if they stick or use a skillet to sear separately.
Add the sliced ginger to the pot and sauté briefly until fragrant.
Return the seared chicken to the pot (if removed). Stir in the soy sauce, sweet soy sauce (kecap manis), ground white pepper, sesame oil, and water.
Close the lid, set to Manual/High pressure, and cook for 8 minutes.
When the cook time ends, perform a quick release. When the valve drops, carefully remove the lid and stir in the scallions.
If the sauce is too thin, turn on Sauté and reduce the sauce for about 1 minute until slightly thickened, then serve immediately.