Step 1

Combine the onion, garlic, thyme, and bay leaves in an Instant Pot. Place the corned beef, fat-side up, on top of the onions; sprinkle with the seasoning packet. In a small bowl, combine the beer and 1/2 cup of water; pour around the beef.

Step 2

Lock the lid into place, place the vent to sealing position, set the Instant Pot to high, and set the time to 1 hour 20 minutes. The Instant Pot will release some steam as it comes up to pressure, then it will seal automatically.

Step 3

When the cooking time is done, allow the Instant Pot to naturally vent for at least 10 minutes. Using a wooden spoon, carefully push the valve open to release the rest of the pressure. Carefully remove the lid.

Step 4

Move the corned beef to a carving board; tent with foil. Remove the cooking liquid from the Instant Pot, reserving 2 cups. Whisk the salt into the reserved liquid. While the meat rests, add the potatoes, carrots, and cabbage to the Instant Pot. Pour the reserved liquid over the vegetables. Lock the lid, making sure the steam valve is in the sealing position. Set to pressure-cook on high for 5 minutes. When the time is up, use a wooden spoon to carefully turn the steam valve to the venting position and let the steam release. Unlock and remove the lid, being careful of any remaining steam.

Step 5

Using tongs or a slotted spoon, remove the vegetables from the cooking liquid and place on a serving platter, seasoning with salt and pepper to taste. Cut beef against the grain, then serve with the vegetables and mustard.