Rinse off your corned beef to remove excess salt and bit of spices. In the pot of your instant pot (or pressure cooker) put the mustard sees, bay leaves, peppercorns, minced garlic the beer and the water. Mix together and submerge the beef in the liquid. If a regular pressure cooker, bring to the boil and cover with cooker lid and venter and when it comes to pressure,lower till it hisses nicely but not hysterically and set a timer (don’t forget!!) for 90 minutes. If using an instant pot, easy peasy. Set the controls to meat/stew for 90 minutes, cover and just make sure it properly comes to temp and the vent is hissing nicely. Wander off, read a book, have a cuppa. Wander back in 90 minutes (for the regular pressure cooker, I advise peeking at the pot from time to time to make sure it doesn’t seem to be hissing too loudly and need a flame adjustment). K. Turn of the instant pot/pressure cooker and let the steam/pressure release naturally. Carefully remove the lid and poke the meat with a wooden skewer or sharp knife to see if tender. If so, let cool slightly (about 15 minutes or so) and carefully remove to a cutting board to rest. YOU MUST let it rest at least 15-20 minutes to redistribute the juices in the meat. If you will eat this right away, cover with a tin foil tent while it rests. If you will eat later or choose to eat room temp, let rest without tin foil. When rested, slice to thickness desired and serve with mustard and wonderful bread or nice with coleslaw and potato salad.