Cut the whole onion into quarters and remove the skins.
Cut the cabbage into quarters and then rinse it well.
Cut the corn cobs into 1 inch discs.
Place the beef shanks, stew meat, onion, black pepper, and salt in the inner pot.
Pour enough water to cover all of the ingredients and it reaches just shy of the max fill line.
Make sure you have your all purpose sealing ring inside the lid of your instant pot.
Place the lid on the Instant Pot, lock it and make sure the toggle is set on sealing.
Press the manual button and select 30 minutes.
Once the Instant Pot beeps let it sit for 10 minutes to do a natural release.
After the 10 minutes has passed release the pressure and open the instant pot.
Stir everything and give the soup a taste. This is where you can adjust the salt level.
Add in the corn and replace and lock the lid. Make sure the toggle is on sealing.
Press the manual button and select 10 minutes.
Once the Instant Pot beeps immediately release the pressure and remove the lid.
Press the cancel/off button and then put in the cabbage. It is a tight fit but the cabbage will cook down and shrink.
Press the Saute button and select the more setting using the adjust button. This should take between 10 and 20 minutes.
Alternatively you can put the cabbage in and then close the lid. Leave the unit on the Keep warm setting and the cabbage will soften up in around 30 minutes to an hour. I like to make the soup in the afternoon and then throw the cabbage in and leave it on warm until dinner time.