Add diced onions and chicken cut into bite size pieces into your pressure cooker.
Whisk other ingredients (except only add 1 tbsp cornstarch) in a bowl and pour that into your pot, stir together.
Close lid and steam valve and set to high pressure for 5 minutes followed by a quick release.
Stir contents. If you want sauce to be thicker, add some of the hot liquid from the pot into a dish (about 4 tbsp) and whisk in 2 tbsp cornstarch until smooth. Then set pot to saute and when bubbling, pour this in and stir.
Allow to cook for 1 minute, stir, then turn off and allow it to sit for a good 5 minutes to thicken more. Serve this over rice topped with diced green onions and sesame seeds.
NOTE: this continues to thicken a lot as it cools too so don't add too much more cornstarch.