take the brisket and trim most of the fat. rub with mustard powder (if you can use Coleman's) and stick in the pressure cooker. add one cup each water and apple cider vinegar (2-3 lb meat) or 1-1/2 cup each (4-5 lb meat) and some splashes of balsamic. seal it up and turn on the burner. When the steam starts to come out of the top, add the little pressure dongle. I cooked mine (4.75 lbs) for about 115 minutes, a smaller meat would be about 90 minutes. The cooker I used is a pressure canner, and so has a pressure gauge on top. I tried to keep the pressure/ temp around 220 degrees. Drink a few beers and put butter on things and before you know it the meat will be done! let the steam disperse naturally (don't push the button, Frank) and try the meat/ try not to eat all of it before the meal. I made mine the night before and heated it back up in a crock pot the next day. ProTip: for leftovers, when you've got a tupperware full of delicious corned beef juice and little slivers of meat, mix it with mashed potatoes or colcannon and cabbage to make a delicious leftover soup!
My uncle Jim has been cooking and perfecting this dish since before I was born. Every St. Pat's we'd get to his house and walk in to that tangy, mustardy smell. Thanks Unk!