Set Instant Pot to Saute.
Once the IP is hot, add the oil.
Add the ground beef, to get a nice sear on it. Cook it without breaking it for 1 minute. Break it up using a wooden spoon as it cooks.
Add the diced onion and minced and cook for another 1-2 minutes, stirring occasionally, until the beef is no longer pink.
Optional: Turn instant pot off by pushing the cancel button. Drain grease and return pot.
Add one cup of water to deglaze the pot, use the wooden spoon to scrape any bits and pieces that stuck to the bottom of the pot.
Add salt, pepper, mustard powder, cheddar soup and broth. Stir well until fully combined.
Add uncooked macaroni to the pot and gently push them using a spatula or wooden spoon so they are submerged in the liquid.
Cover and seal the lid. Make sure the valve points to Sealed. Change setting to manual and adjust time to 4 minutes on High Pressure.
Once Instant Pot beeps to show that it's done, wait 5 minutes and after that do a quick release, by changing the position of the valve to Vent. Carefully remove cover and stir.
Remove the lid and set IP to saute.
Add your sour cream and stir to combine.
Turn off the Instant Pot.
Add Velveeta cheese and shredded cheese. Place back the lid for 1 minute, to melt the cheese.
Remove lid and stir slowly to fully combine the cheese into the sauce. Based on preference you can add more cheese. If the sauce is too thick, select Saute and add a little chicken or beef broth, simmer and turn off.
Serve topped with chopped parsley.
When reheating on the stove top, either add some milk, cream or broth, to make it creamier.