Dice the stew meat into bite-sized pieces and liberally salt and pepper.
Dice the onions into small pieces.
Clean and quarter the mushrooms.
Set the Instant Pot (pressure cooker) to saute.
Add olive oil to the pot.
Working in small batches, brown the beef. Once browned, set pieces in a bowl or on a plate.
Add onions to the pot and cook for 2-3 minutes.
Add mushrooms into the pot with the onions and cook for another 3 minutes.
Stir in the flour.
Add the mustard, beef broth, and wine.
Place beef and any juices that are on the plate into the pot.
Cover the pressure cooker, set it to manual mode, and cook for 15 minutes with automatic release.
When the beef stroganoff is done, open the lid and reset the mode to saute.
Mix the cornstarch and water until it's a creamy paste.
Stir the cornstarch water paste into the pot to thicken the gravy.
Remove the inner pot from the pressure cooker.
Whisk in sour cream.
Serve over cooked egg noodles and garnish with fresh parsley.