Once oil heats up, add ground beef and onions to IP, cook until no longer pink and onions are translucent.
Drain and return to pot.
Sprinkle meat mixture with seasoning, garlic salt and pepper. Stir.
Pour green enchilada sauce, beef broth and Rotel into pot.
Add pasta shells, stir.
Close and lock lid, turn vent to the sealing position, press Manual or Pressure Cook,High Pressure and set the cook time for 1 minute. When pot comes to pressure (about 15-20 minutes), turn off and use quick release. That is enough time for the pasta to cook because the shells are so small.
Open lid once the float valve drops, add cream cheese, sour cream and shredded cheese, stir and serve.