Generously salt and pepper short ribs. I always use Kosher salt.
Heat Instant Pot on saute and add 1 tbsp olive oil. Brown ribs on all sides. Let them sit on each side without moving them so they have time to brown. Around 10 minutes.
Remove ribs. Add a little more oil if pan is dry. Add onions and garlic and saute in all that goodness in the bottom of pan. Saute for about 5 minutes then add all ingredients except cornstarch. Nestle ribs back down in the sauce.
Put lid on to sealed and turn Instant Pot to the stew setting. Set timer for 30 minutes. Once the timer beeps let the pot naturally release and do not open. This is when the ribs get tender. If you use bone in ribs you will need to add 15 minutes to the time.
Remove the meat to a plate and turn pot to saute. Add the cornstarch with 3 tbsp water in a small bowl and whisk well. Add to sauce in bottom and pan and stir well. Get all those brown bits up from the bottom of the pan. Let cook until desired thickness is reached.
Serve with cauliflower mash, mashed potatoes or rice. Salt and pepper to taste.