For a three-pound chunk of tough meat you need to sear it thoroughly to start and get up to 15 pounds of pressure and cook for 30 minutes. Let cool until the rattle can be removed and add the veggies. Start the heat back up and when it gets to pressure turn off the heat and move to a cold burner.
When it gets cool enough to remove rattle, and then lid, the meat will be very tender, guaranteed, and the veggies will be overdone.
That is the PC recipie I was raised on. My mother cooked most everything in a pressure cooker. My wife's family only used them for canning, but they always lived at elevations of about 200 ft, so they didn't need them so much. It wasn't until I moved her to Colorado that I even got her to try one.
You can make some great tamales in one too, with a rack and just a little bit of water.
