Select [Saute] to pre-heat the pressure cooker on saute mode. When the word “Hot” appears on the display, add cooking oil to heat until shiny. Saute the garlic and onion until soft.
Add the beef shanks, whole black peppers, fish sauce, broth, and yellow corn in the Instant Pot®. Close the lid and set the steam release handle to the Sealing Position. Select [Pressure Cook] and [High] then use the [+] or [-] buttons to set the time to 35 mins.
Once done, turn the pressure release valve for Quick Release of pressure. Either use mittens or a wooden spoon to do this. Open the lid and keep the contents to a boil by selecting [Saute]. Add the pechay and cabbage, cooking until tender.