Heat Instant Pot on sauté mode, and add olive oil.
Season beef with salt and pepper, then sear in Instant Pot until browned on all sides.
Add diced onions, beef broth, tomato paste, Worcestershire sauce, Dijon mustard, and dry onion soup mix.
Lock the lid, and set it to high pressure for 50 minutes (120°C / 250°F).
Naturally, release pressure for 10 minutes, then quick release.
Remove the beef from the pot, wrap it in aluminum foil, and set aside.
Add potatoes and carrots, lock the lid, and cook for another 3 to 5 minutes on high pressure (120°C / 250°F).
Naturally, release pressure for 5 minutes, then quick release. Plate out the vegetables and set aside.
Mix cornstarch and cold water, and stir into Instant Pot until thickened.
Shred the beef with the help of a fork and set it on the serving platter. Set the vegetables and pour gravy all over.
Garnish with parsley before serving. Enjoy your Instant Pot beef roast!