First, put the water, garlic, onion, and pickling spices in the Instant Pot. Grab the rack and place in the Instant Pot.
Put the corned beef in the Instant Pot on top of the rack. You want the fat-side of the corned beef facing up.
You can now pour the beer over top of the corned beef.
Put the lid on the Instant Pot and seal the valve.
Set the Instant Pot to "Manual" high pressure for 85 minutes.
Once the timer is up, allow for a natural release of pressure for around 20 minutes.
You can then quick release remaining pressure. Put the corned beef on a cutting board, and then cover it with foil. This will help ensure it stays warm.
Take the Instant Pot and strain out the liquids and get rid of any other solids.
Now, add in 1.5 cups water and then add in the cabbage pieces, carrots, and potatoes.
Seal the valve on the Instant Pot once again and put the lid back on.
Cook this on "Manual" high pressure for about 4 minutes. Quick release the pressure.
Cut up the corned beef, going against the grain. You can add some of the cooking liquid that is reserved on top for more juicy corned beef.
If you want the parsley, put that on top of the vegetables.
You now have a finished corned beef and cabbage meal ready to eat!