Turn the pot on to Sauté setting. When the pot is hot, add the oil.

Add the Beef cubes in one layer (you will probably need to cook in 2 batches). Brown both sides lightly so they get some color. Don't cook them all the way through.

With all of the browned beef in the pot (still on sauté), add the water/broth, and stir, scraping up any brown bits from the bottom of the pot (deglaze).

Add the soup mix and stir well.

Add the Cream of mushroom soup on top of the meat, and do not stir it. Just let it sit in a pile on top (this is so the mixture isn't too thick to come to pressure, and you don't get the BURN message).

Place the lid on and set the steam release knob to the sealing position.

Cancel the sauté feature and press the Pressure Cook/Manual button (or dial), and the + or - button (or dial) to select 25 minutes.

When the cook cycle is finished, let the pot sit undisturbed for 10 minutes (10 minute natural release). Then turn the steam release knob to the Venting position to manually release the remaining steam/pressure (Quick Release).

When the pin in the lid drops down, open the lid and give the beef mixture a stir. Turn off the pot, then turn on the Sauté function to the Low setting, and add the noodles. Stir them in and submerge them.

Cover the pot with a glass lid. Let the noodles cook until they are tender, stirring occasionally to make sure they don't stick, for about 5-8 minutes. 

When the noodles are done to your liking, turn off the pot and serve. If you are adding the sour cream, you can stir it in before serving, or top each serving with a dollop.