Cut the brisket in half so it will fit in the bowl of your Instant Pot. Rinse it with cold water. Place the trivet into the instant to prevent it from sticking to bottom. If it isn't too large, you might not need to cut it. Place it in, fat side up.
Add the seasoning packet, onion, garlic cloves, bay leaf and water.
Lock lid in place and set to manual high pressure for 45 minutes.
Use the quick release method and remove corned beef brisket. Set aside and tent loosely with aluminum foil to rest.
Layer the potatoes, carrots and then cabbage over the cooking liquid. Place lid back on and set to manual high pressure for 3 minutes. Use the quick release method.
Slice the brisket against the grain and plate along with cooked vegetables.
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