Instant Pot Salisbury Steak with Mushroom Gravy

Combine bread crumbs, onion, egg, parsley, Worcestershire sauce, and garlic in a large bowl. Mix everything together thoroughly until well combined. Add beef and pork to the mixture, stirring gently to incorporate. Divide the mixture into 8 equal parts and shape each portion into a patty. Cover the patties with plastic wrap and refrigerate for 1 hour to allow the flavors to meld. Remove the patties from the refrigerator about 30 minutes before cooking.

Heat a multi-functional pressure cooker, such as an Instant Pot, over medium-high heat. Add oil to the pot and sauté the patties in batches to prevent overcrowding. Cook the patties for 2 minutes on each side, or until browned. Transfer the cooked patties to a plate and set them aside.

Add more oil to the pot if necessary, then sauté sliced onions until they are browned and fragrant, about 2 minutes. Add sliced mushrooms to the pot and cook for an additional 2 minutes.

Pour a small amount of wine into the pot, scraping up any browned bits from the bottom with a wooden spoon. Add broth, tomato paste, salt, and pepper to the pot, stirring everything together well. Return the cooked patties to the pot and stir them into the sauce.

Close the lid of the pressure cooker and lock it in place. Follow the manufacturer's instructions to set high pressure and a timer for 15 minutes. Allow 10-15 minutes for the pressure to build up.

Release the pressure from the pot using the natural-release method, according to the manufacturer's instructions. This may take anywhere from 10-40 minutes. Once the pressure has been released, unlock and remove the lid.

Combine 4 tablespoons of broth with cornstarch in a small bowl. Stir the mixture until it is smooth and free of lumps. Slowly add the cornstarch mixture to the pot, stirring constantly with a spoon. Heat the pot over medium-high heat and cook until the sauce has thickened, about 5 minutes.