Make Patties: In a large bowl, combine the beef, breadcrumbs, egg, Worcestershire sauce, salt and pepper, using your clean hands. Divide into 6 equal pieces and form each one into oval patties.
Cook Patties: In a large skillet add the olive oil and heat over medium-high heat. Add the meat patties and fry on both sides until browned, about 3 minutes per side. Transfer the patties to a plate. *These can be browned in the instant pot as well using the sauté function, but I find it easier to just use a skillet.
Add Ingredients: Place the onion and mushrooms in the instant pot, then layer the beef patties over the mushrooms. Combine the beef broth, tomato paste, Worcestershire sauce, salt and pepper and pour over the steak.
Cook: Close the lid (follow the manufacturer’s guide for instructions on how to close the instant pot lid). Cook on high pressure (Manual setting) for 18 minutes.
Make Gravy: Once the Instant Pot cycle is complete, quick release. Remove patties from the instant pot and turn the Instant Pot to the Saute setting. In a small bowl whisk the cornstarch with the 2 tbsp of water, pour this over the mushroom gravy in the IP. Stir everything well and cook for a couple more minutes until the gravy thickens.
Finish: Add the steak patties back to the Instant pot and spoon gravy over the top. Cook for another minute until the meat patties warm through.
Serve: Garnish with parsley and server over mashed potatoes, rice or noodles.