Using a sharp knife, slice the pork so that, as much as possible, the meat and fat are in separate chunks. Cut the fat chunks small and the meat chunks into large 4-inch pieces.
In the Instant Pot, combine the pork, onion, garlic, bay leaves, thyme, peppercorns, and water.
Secure the lid on the pot. Close the pressure-release valve. Select Pressure Cook/Manual and set the pot at High Pressure for 30 Minutes. Allow the pot to sit undisturbed for 10 Minutes, then release any remaining pressure.
Remove the pork chunks, separating the fat from the meat where possible. Most of the fat will have rendered into the juices at the bottom of the pot.
Strain the broth through a sieve, discarding any solids. Place the broth in the freezer for 15 to 20 Minutes to allow the fat to rise to the top, or use a fat separator cup. Set the fat aside.
Meanwhile, using a stand mixer, shred the pork into fine threads. Do not allow it to get pasty. Mix in the lemon juice, mustard, nutmeg, and salt to taste. Add a little broth if needed to keep the meat moist.
Divide the meat into eight small ramekins. Tamp the meat down into each ramekin. Scoop out some of the fat you set aside, and top each ramekin with the fat. Chill for at least 4 Hours.
To serve, bring the ramekins to room temperature and serve with chunks of bread.
Tip: If you’re short on time, skip the step where you separate the fat from the broth. It is more traditional, but I usually skip this step and just ladle the hot broth, with the fat, on top of the meat before chilling.