Combine the ground beef with the garlic salt, black pepper, breadcrumbs and egg. Mix until everything is throughly combined. Divide into 4 even sized portions thenshape into 4 patties
Set the pressure cooker to saute, add the oil, then place the patties inside. Sauté for 5 minutes. Carefully flip over and sauté for about another 5 minutes so outsides are no longer pink. Carefully remove the patties and set aside. Add a bit of your broth and deglaze your pot now.
Add the onion and sauté until it begins to soften, about 4 minutes making sure to stir often. Next add the mushroom slices and also sprinkle in a pinch of salt and black pepper, sauté for 4 minutes while stirring often.
Turn pot off. Then pour in remaining broth and the Worcestershire sauce and give the ingredients a good stir. At this time taste the broth mixture and if needed add salt to taste.
Place the patties back into the pot, careful as to not break them. Then put the lid on the pressure cooker, set to high pressure for 15 minutes. Once cooking time is finished do a quick release
Carefully remove the patties and set aside. Mix the cornstarch with the water until you have a smooth mixture. Turn pressure cooker to saute, then pour in the cornstarch mix and stir until well combined. Simmer until the broth has a gravy consistency, then cancel sauté function.
Serve meat on top of mashed potatoes or butter noodles with a drizzle of the gravy inside your pot.