Cut the short ribs into 1½-inch cubes. Pat dry with paper towels. Season with salt and pepper.
In an electric pressure cooker with the “saute” setting (cook over medium-high heat in a stovetop pressure cooker), warm up the sesame oil. If your electric pressure cooker doesn’t have a “saute” function, use a large pan and cook over medium-high heat on the stove. Sear the short ribs on all sides until nicely brown. Transfer the meats to a plate. Set aside.
Remove most of the fat and brown bits with paper towels, but leaving ½ tablespoon oil in the pan. Add onions and cook until just tender. Add ginger and garlic. Stir and cook for a minute. Pour in the seasoning and cook for 2 minutes.
Combine all the ingredients in the pressure cooker. Stir and mix well. Cover and lock the lid. If using electric pressure cooker, make sure the pressure release valve is at the “sealing” setting, not “venting”. If using stovetop pressure cooker, bring to high pressure over high heat. Once it is at high pressure, reduce to low heat.
Cook the meat and vegetables for 25 minutes. When cooking is done, the “keep warm” button will be on (turn off the heat for stovetop pressure cooker). There are two ways to do it. You can either release the pressure naturally by doing nothing, about 20 – 30 minutes or you can release pressure slowly or carefully by opening the vent. Make sure you read the manual book to know how to do it safely.
Open the lid and transfer the meat and vegetables to a serving plate. Top with a few tablespoons of sauce and green onion. Serve immediately with hot steamed rice.