This is an optional step, but if you have time and can plan ahead: pour the red wine over short ribs in a large bowl, cover with plastic wrap and marinate in the refrigerator, 8 hours to overnight.
When ready to cook, season ribs with salt and pepper.
Select the "Saute" setting on an electric pressure cooker and Adjust it to High. Once it reads HOT, add olive oil.
Add 2-3 short ribs to hot oil, you want to sear the short ribs in batches, in one layer in the Instant Pot.
Cook until the bottom is browned, about 8 minutes. Cook a few more minutes on the other side. Transfer browned short ribs to a plate and cover with foil. Repeat cooking with remaining short ribs.
Once the ribs have been seared and are resting now covered in foil on a plate, add to the pot the crushed garlic, cook for 1 minute. Add the rosemary and thyme, stir and cook for 1 minute.
In a large cup, mix together 1 cup of red wine, the soy sauce, and the Worcestershire sauce. Add the sauce to the pot to deglaze it. Using a wooden spoon scrape the bottom of the pot really well to remove any pieces the stuck to it.
Add one more cup of wine.
Add one layer of short ribs, the quartered onion, and the carrots. Top with the remaining ribs and the remaining wine. Add bay leaves.
After you added all the wine if the second layer of short ribs is not covered in liquid at least to its half than add one cup of beef broth. The bulk of the ribs need to be submerged in liquid.
Ensure that the total volume does not go above the maximum fill line.
Close and seal the pressure cooker. Turn the venting knob on top to "Sealed".
Press the "Manual" button and set the timer for 40 minutes on High Pressure. For bone in, larger short ribs, add 15 more minutes to the cooking time. Note: the pot has a lot of liquid, so it may take over 20 minutes to come to pressure.
When it beeps do a natural pressure release for 15 minutes and then release any remaining pressure.
With tongs, remove ribs to a platter and cover with foil to keep warm.
Optional: Use a fat separator or a mesh strainer to separate the fat from the juices, keep in mind that you won't be able to do this if you added the carrots. If you added the carrots, skim the sauce off with a spoon to remove the fat.
Remove and discard the bay leaves. Return juices to the pot.
In a small bowl, combine molasses and balsamic vinegar and add it to the pot.
Select Sauce function and Adjust to Medium heat. Simmer the sauce for about 30 minutes, stirring occasionally until it thickens.
If the sauce is not as thick as you want, in a small bowl, combine cornstarch and water and add it to the pot, stir to combine and bring to a boil. Turn pressure cooker off.
Optional: Add ribs back to the pot and gently coat with the sauce. Put the lid back on the pressure cooker and let the ribs absorb some of the sauce for about 10 minutes.
Serve over mashed potatoes.