Turn pressure cooker to saute mode and add olive oil. Add roast when hot.
Brown each side, turn pot OFF, remove meat from pot and deglaze the pot (add 1/2 c. of your beef broth and scrape the bottom well to remove all stuck on meat).
Return meat to pot, add onions, seasonings and rest of broth.
Close lid and steam valve. Set to high pressure for 50 minutes. (timing is average but varies slightly depending on size and thickness of meat piece you have)
Do a natural release for 25 minutes, then let out rest of steam.
Add potatoes, carrots and mushrooms. Put lid back on and close steam valve.
Set to high pressure for 6 minutes, quick release when done.
Remove vegetables and meat. If you want to make gravy leave liquid in pot, set to saute and whisk together in a small bowl 2 tbsp. cornstarch with 3 tbsp cold water until smooth and add in. Stir until it thickens, turn pot off.