Peel and slice onions. Spread onions on bottom of the Instant Pot along with coriander seeds and peppercorns. Discard spice packet from brisket if it comes with one. Place brisket on top of onions. Season generously with salt and pepper. Pour in beef broth and beer.
Set to cook on high pressure 85 minutes. Let release naturally at least 15 minutes. Transfer brisket to serving platter and cover.
Cut carrots into 3" pieces. Cut cabbage into 8 wedges. Add both to Instant Pot. Season with salt and pepper. Cook on high pressure 2 minutes. Let quick release. Thinly slice corned beef against the grain and serve with carrots and cabbage. Serve drizzled with any cooking liquid from Instant Pot and mustard on the side, if desired.
Tip: If the corned beef comes in pickling liquid, just wipe off before adding to the Instant Pot.
Source: Hannaford fresh Magazine, March April 2024