Place Corned Beef Brisket and 1 cup water in the Instant Pot. If seasoning packet is included with corned beef brisket, pour it over the beef brisket after water is added.
Close and lock pressure cooker lid. Use beef, stew or high-pressure setting; adjusting time to 70 minutes.
When time is up, use the quick release feature to release pressure; carefully remove lid. Remove beef.
Add potatoes, carrots and cabbage to pressure cooker. Close and lock pressure cooker lid.
Use beef, stew or high-pressure setting, adjusting time to 3 minutes. Use the quick release method again once time is up.
Remove fat from brisket, if desired. Carve brisket into thin slices across the grain.
Combine butter, salt and pepper in small bowl. Drizzle over vegetables. Serve brisket with vegetables. Enjoy!