Add the beef back to the pot.
Add the remaining ingredients, starting with the onion and finishing with the butter.
Close the lid and seal the valve.
Cooking: if you have a pot roast that has been cut into pieces, and the pieces are no more than 2 inches thick, cook for 75 minutes on High Pressure. If the beef is thicker than 2 inches, mine was 4 inches at the center, cook for 100 minutes.
Once the Instant Pot beeps, do a 15 Minute Natural Pressure Release. Release manually the remaining pressure.
Open the lid and check if the beef is tender enough to shred. If it's not, cook for another 15-20 minutes on HP with a 15 min NPR.
Remove beef from the pot and add it to a large serving deep dish.
Place a fine mesh over a mixing bowl and sieve the cooking liquid from the pot. Add one cup of liquid to the beef and return the rest to the pot.
Shred beef and cover with aluminum foil, place a towel on top to keep it warm.