Set Instant Pot to saute. When it says HOT, add oil.
Add ground beef, onions and garlic to pot. Cook until meat is browned, stirring to break up meat. Season with salt, pepper, thyme and Worcestershire sauce as it is cooking.
Add tomato paste, water and beef base. Stir to scrape up any bits stuck to the bottom of the pot. Add elbows. Press cancel to stop Saute.
Lock lid in place and seal valve. Cook on high pressure for 4 minutes. (Cook time may vary with the kind of pasta you choose to use). Quick release the pressure. Stir in half of the cheese. Serve remaining cheese on the side.