Add the ground beef, minced onion and garlic powder to the base of the Instant Pot insert. Press Saute and Adjust to More, and brown the ground beef. Drain, if needed, and add back to the insert.
(Option #2: brown the ground beef in a skillet, cook the pasta and liquid in the IP, then stir in the meat after the pasta has cooked and the cheese is mixed in.)
(Option #3: if you have frozen, pre-browned ground beef, you can add it frozen on top of the pasta and liquid.)
Add the dry pasta onto the browned ground beef.
In a mixing bowl, whisk together the chicken stock and mustard, then pour over the pasta and meat. Move the pasta around, if needed, to make sure all the pasta is "under water."
Set on Manual, High, and cook for 6 minutes.
Let naturally release for 5 minutes, then release the remaining pressure.
Stir the pasta and ground beef and mix it up well. Then add the butter, cream and shredded cheese. Stir to combine. Season if you wish, with one of these options: Italian seasoning, Cajun seasoning, taco seasoning, Ranch dressing mix.
Serve Instant Pot Hamburger Helper with favorite veggies or salad.