Add canola oil to the instant pot. Using the saute setting, sear all sides of your short ribs for 3 - 5 minutes or until browned
remove short ribs from pot. They won't be fully cooked.
Add onions, garlic, and mushrooms to pot. Cook for 3 - 5 minutes, until onions are translucent and mushrooms have softened
add salt and pepper to taste. Stir in tomato paste.
Add vinegar and red wine to pot, and deglaze. Make sure to scrape up all brown bits! Bring to simmer
Once it's simmering, add the short ribs back to pot, nestling in the mushrooms and onions
Lock lid on, and use pressure cook mode for 65 minutes at high pressure (50 if boneless)
let it naturally release steam for 15 minutes. Remove short ribs to separate plate
In a small bowl, whisk together cornstarch and water. Set instant pot to saute, and stir in cornstarch mixture. Cook until it reaches light gravy consistency, about 2 minutes.