I cut up an onion into fat slices, put those in the bottom of my pressure cooker. Open the spice packet that usually comes with the corned beef and sprinkle over the onions. Rinse the meat well in cool water, place atop the onions, pour in two 12 oz. homebrewed beers (stout this time), put on the top and set the digital timer on the PC to 75 minutes on high.
Let drop pressure naturally, remove meat, add some red potatoes and onions that have been peeled but don't remove the root end, quarter them through the root end (keeps the onion together pretty well this way) and turn the pressure on High for 4 to 5 minutes, depending on size of potatoes. Quick-release pressure when done. I do the baby carrots separately in the MW with some butter and a squeeze of honey, and I make coleslaw 'cuz I'm just not that wild about steamed cabbage.
Alternatively, if I think about it far enough ahead, I do the corned beef in the sous vide all day at 185*.