Quick, easy to use and nearly foolproof, pressure cookers take the low-and-slow out of tenderizing and make cooking shredded chicken a task you can finish in minutes instead of hours. You usually have to braise chicken at a low temperature for a few hours to get it to where it shreds effortlessly, but not in a pressure cooker. Pressure cookers raise the boiling point of water, so the chicken cooks at a higher temperature and at least twice as fast without losing moisture. As a bonus, the cooking liquid turns into a rich, gelatinous stock while the chicken cooks.
Spread a 1-inch layer of mirepoix in the bottom of the pressure cooker, minus the celery. Mirepoix, or diced carrots, onions and celery, is a classic flavoring combination for chicken, but celery breaks down in the pressure cooker and loses its flavor quickly.
Add aromatics to the pressure cooker. Classic aromatics include a bay leaf, a few parsley stems, a couple thyme sprigs and black peppercorns, but you can add ingredients that go with what you'll use the chicken for. For example, if you're going to use the chicken for fajitas or tacos, you might add chilis and crushed garlic cloves.
Place the chicken on top of the mirepoix. You can use any parts of the chicken you like, but you get the best texture for shredding from dark meat. If you want to use white meat, use a mix of 2 parts chicken legs to 1 part chicken breast so you'll get the moistness you need to shred the meat.
Pour cold water over the chicken until it just covers it, but doesn't exceed the pressure cooker's fill line, usually at 2/3 full. You need at least 2 cups of liquid if you want to a broth.
Add dried spices and fresh herbs to the water, if desired. You don't need to stir the herbs and spices into the water. Like aromatics, choose spices that complement your chicken dish. For example, you might add coriander, cumin, paprika and oregano if you're going for Southwestern flavors.
Sprinkle kosher salt into the water to taste. Since you can't taste the liquid for seasoning, follow a guideline of about 1/3 to 1/2 tablespoon of salt per pound of chicken. Secure the lid and place the cooker on a large burner.
Set the heat to high and let the cooker reach full pressure, about 15 to 20 minutes. Reduce the heat until you can barely hear air escaping.
Cook the chicken for about 30 minutes. Move the pressure cooker to the sink and run cold water over the lid. The steam will dissipate quickly and the lid will unlock when it's safe to open, about 30 seconds.
Remove the chicken with tongs and set it in a shallow dish. Strain the broth from the pressure cooker through a colander lined with cheesecloth and into a food container. Let the chicken rest until cool enough to handle.
Shred the chicken by hand in the shallow dish or scrape it from the bones and shred it with forks.
Serve the chicken as-is, or store it in an airtight container for 2 or 3 days in the refrigerator, or for a few months in the freezer.