Press the sauté button, add oil and allow it a minute to heat up. Add the cumin seeds, mustard seeds and serrano pepper. Once the cumin seeds brown, add the chicken and spices and stir-fry for 2-3 minutes to coat the chicken.
Add vinegar and onion masala.
Secure the lid, close the pressure valve and cook for 5 minutes at high pressure.
Naturally release pressure or quick release after 10 minutes.
Garnish with cilantro and serve.