Cut the chicken into 1-inch cubes, and toss the cubes with cornstarch to coat. Prepare all the herbs and vegetables.
Set the Instant Pot on Sauté. Pour in the sesame oil. Add the onion, garlic, and ginger. Sauté for 2 minutes, then add the chicken pieces. Stir and brown for 3-5 minutes, until the chicken pieces are golden on most sides.
Add the brown sugar, soy sauce, sherry, chili garlic sauce, and 2 tablespoons water to the Instant Pot. Stir well to coat the chicken.
Cover and seal the pot. Set on Pressure Cook High for 3 minutes. Turn off the pressure cooker, and perform a Quick Release. Once the steam valve button drops, and it is safe to open, remove the lid. Stir the sesame chicken and sprinkle with sesame seeds and scallions. Serve warm with rice, quinoa, or with steamed vegetables.