Fireworks Instant Pot corned beef with steakhouse butter

I love this meal. Not sure if it's the salt from the meat or what but I'm even down with the boiled cabbage and butter. It must be the butter! You can't have enough in this meal. The butter is great on all the veggies here. You can use store-bought brined brisket or make your own by following the recipe here.

You can use the slow cooker too, but since I'm practicing with the Instant Pot it was fun to try. It worked out great. Cook the veggies separately so they don't turn to mush. This should serve 6 just fine.

1 large onion, quartered
1 3-4 lb beef brisket 
5-6 red potatoes
5-6 large carrots (not the baby ones), peeled and cut into 2-3 inch chunks
1 head green cabbage (purple cabbage turns everything a weird bloody color)
4 cups water
2 Tbs pickling spice
1 Fireworks Steakhouse butter burst
Put the onion in the bottom of the instant pot, place the beef on top. If you bought it brined from the store, throw in the pickling spice on top. Add the  water and make sure the valve is turned to seal. Set the instant pot to high and cook for 80 minutes.
Once the time is up, carefully turn the valve to release and let the remaining pressure out. Remove the beef and onions from the instant pot and set it aside to rest.
Take out 2 cups of the water, discard. Then add carrots, potatoes and cabbage. Make sure the valve is turned to seal. Turn the pressure cooker to high for 5 minutes. Once the time is up then release the pressure. Once the pressure is released, open the lid and take out the veggies and put them on the outer part of your platter. Slice the meat against the grain and lay it down in the center of your platter. Add dollops of butter all around the potatoes, carrots and cabbage. Serve with any remaining butter. Sizzle. Spread. Boom.