Sprinkle salt and pepper onto the chuck roast beef.
Turn the instant pot on [SAUTE] and set for 30 minutes. Wait until the instant pot reads “hot”, then add a generous amount of olive oil in the pot. Brown the chuck roast beef on all sides (it is best to work in 3-4 batches. Do not overcrowd so you can get a nice crust. Add more olive oil, if needed, to prevent the beef from sticking) then set it aside in another bowl. Add onion; cook and stir for 2-3 minutes or until the onion is soft.
Press [CANCEL] and deglaze the pot with red wine, beef broth and Worcestershire sauce. Be sure to scrape any bits stuck to the bottom of the pot with a rubber spatula.
Stir in garlic, and browned chuck roast beef. Layer on tomato paste and thyme on top (do not stir). Close the lid; make sure the knob is turned to “sealing”. Press [PRESSURE COOK] (or “manual” for older models) and set it on high pressure for 20 minutes.
Once it is done cooking, let the pressure naturally release (just leave the pot alone) for 10 minutes and then quick release the rest of the pressure by turning the knob to “venting”. Open the lid; take the thyme out (if using fresh thyme). Then, layer on the carrots, celery, potatoes, and mushrooms. Close the lid; make sure the knob is back to “sealing”; press [PRESSURE COOK] (or “manual”) and cook on high pressure for an additional 6 minutes. It’s best to naturally release the pressure but if you’re in a rush let it naturally release for at least 10 minutes so the beef doesn’t dry out.
While everything is cooking...in a small bowl, mix cornstarch and water until well combined.
It’s best to naturally release the pressure when it is done cooking but if you’re in a rush, let it naturally release for at least 10 minutes so the beef doesn’t dry out. Open the lid and press [SAUTE] for 2 minutes. Add in cornstarch mixture to thicken up the sauce; add salt and pepper to taste.