These Instant Pot short ribs are fall-off-the-bone tender in less than an hour under pressure, and the best part is the mashed potatoes cook AT THE SAME TIME in the Instant Pot!
Use a paper towel to wipe short ribs dry and also to remove any blood or bone fragments.
Season all sides of the short ribs with 1 teaspoon salt and pepper. Working in batches, place 3 to 4 short ribs in hot Instant Pot and brown on all sides, about 3 minutes per side. Remove to plate and repeat with remaining short ribs. (takes about 30 minutes total)
If there is a lot of oil/fat in the pan at this point, carefully remove all but about 1 tablespoon. Add onion, celery, and carrots and cook, stirring constantly for about 3 minutes, or until onions are translucent. Add garlic and cook for about 1 minute, stirring, or until fragrant.
Add wine and scrape bottom of the Instant Pot, making sure to remove ALL brown bits (will prevent a burn notice later). Cook for 2 to 3 minutes or until wine is reduced by about half.
Add 1 cup beef broth, balsamic vinegar, brown sugar, Worcestershire sauce, bay leaf, paprika, thyme. Stir to combine and then carefully add short ribs back into the pot, as well as any juices that have collected on the plate.
Place a small stainless steel bowl (or cake pan) on top of short ribs and add potatoes to bowl. Sprinkle with ½ teaspoon salt.
Secure lid and turn valve to seal, if necessary. Set to Pressure Cook (or manual, high pressure depending on model) for 42 minutes. Let pressure naturally release for 10 minutes before releasing remaining pressure.
Carefully remove pan of potatoes, drain if needed, and transfer to a larger mixing bowl. Mash with butter and milk until desired consistency is achieved.
Remove short ribs from Instant Pot and place on a plate. Turn Instant Pot to Sauté mode. In a small bowl, whisk together cornstarch and 2 tablespoons beef broth. Pour into sauce in Instant Pot and stir to combine. Let the sauce simmer until thickened. Taste and season with salt and pepper.
Turn Instant Pot to warm and place short ribs back in sauce to keep warm until ready to serve over mashed potatoes.
Garnish with chopped fresh chives or parsley, if desired.
Notes
If a thicker sauce is desired, add an additional 2 tablespoons broth, mixed with 1 tablespoon cornstarch.
If desired, you can cook the short ribs without the potatoes. Cook time remains the same; it will take a bit less time to come to pressure.