Season the beef with salt and pepper and brown in small batches. Remove from the Instant Pot and set aside.
Pour ½ cup of the beef stock into the pot and scrape any brown bits off the bottom of the Instant Pot.
Return beef to Instant Pot and add remaining ingredients (except cornstarch) to the pot and close the lid.
Turn on to MANUAL. Choose HIGH PRESSURE and set the time to 15 minutes. Once time is up, quick-release pressure.
Combine cornstarch and water in a small bowl. Turn the Instant Pot on to SAUTE to bring the broth to a boil. Whisk in cornstarch until the gravy reaches desired thickness.
Taste and season with salt and pepper. Discard bay leaf and serve over mashed potatoes.
Notes
The onion soup in this recipe is a canned condensed soup found in the soup aisle at your local grocery store.Leftovers will keep in the refrigerator for up to 4 days.