Add 1 tablespoon of the oil to your Instant Pot. Press the "sauté" button and once the oil is hot, add half the beef. Brown the beef on all sides (I find this easiest to do with tongs). I like to do two batches so the meat isn't crowded and browns nicely.
Once the beef is seared, transfer it to a plate and set aside. Repeat for the second batch (use the second tablespoon of olive oil).
Add the onion to the IP and sauté for 3-4 minutes (add a splash more oil if needed).
Stir in the garlic and cook for about 30 seconds.
Add about a cup of the beef broth to the IP and scrape any brown bits from the bottom thoroughly (a wooden spoon works well). This is important as it'll help prevent getting an IP burn warning.
Stir in the rest of the broth, tomato paste, Worcestershire sauce, salt, and pepper until smooth.
Add the remaining ingredients except for the cornstarch (including returning the beef to the pot).
Close the lid and set the valve on "sealing", and cook on high pressure for 35 minutes. It will take 10-15 minutes for the Instant Pot to get up to pressure.
Once the countdown is done, let the pressure release naturally for 10-15 minutes, and then do a quick release for the rest of the pressure. Mix the cornstarch with 2 tablespoons of cold water and add the slurry to the IP. Give it a good stir and let it thicken up for a few minutes (you can put the "sauté" button back on if needed to activate the cornstarch). Season with salt & pepper to taste and enjoy!