Shred the cheese and set it aside to allow it to come closer to room temperature.
Set the instant pot to saut� and add the vegetable oil.
Add the ground beef, cook and crumble for about 5 minutes.
Add the onions and cook for another 3-4 minutes, until the onions are soft and translucent and the meat is cooked through.
Add the garlic, Worcestershire sauce, tomato paste, salt & pepper, cook for 2 more minutes
Pour in 1/4 of the beef broth and scrape the bottom of the pot to release the cooked pieces of beef that are stuck. This will give the sauce extra flavor but also prevents the burn indicator from turning on during pressure cooking.
Add the rest of the broth and submerge the macaroni into the sauce so that it�s completely covered.
Lock the lid, seal the valve, and set the pressure cooking time to 5 minutes.
Once 5 minutes are up, quick release the steam valve.
Gently stir in the cheese until well combined.
Garnish with chopped parsley or Parmesan flakes if desired, and serve.