With pork, the premium cut is its loin. It's lean, tender, mild in flavor and boneless, much like a chicken breast, and it's equally easy to work with. Unfortunately it's also relatively bland, and becomes dry and unappealing unless it's cooked quickly. For slow cooking, the humble and inexpensive pork shoulder emerges as a better choice. Cooked at temperatures of 250 degrees Fahrenheit or lower for an extended time, the shoulder becomes remarkably lush and tender.
The pork shoulder's anatomy has much to do with the choice of cooking technique. It's a complex roast, with bones, connective tissues, fat and a network of muscles running in different directions. If it's cooked quickly it can be stringy and chewy, but the cut comes into its own when slow-cooked. Whole shoulders make a very large roast, often 12 pounds or more, so they're usually cut in half for retail purposes. The upper portion of the shoulder is usually referred to as the butt or Boston Butt, while the lower portion is usually sold as a fresh picnic or shoulder arm roast. Any of these can be slow-cooked.
Cooking times are variable for shoulder roasts, depending which cut you've purchased and how you're cooking it. At 250 F or lower, shoulder roasts will typically require 1 1/2 to 2 hours per pound. If your roast is deboned and tied it will cook more quickly, so expect your cooking times to be at the shorter end of that scale. Bone-in roasts take longer, especially if you leave the thick rind of fat in place to protect the meat from drying. Those cooking times assume you're cooking the roast to well-done to take full advantage of the shoulder's character.
Importance of Temperature
In 2011 the USDA lowered the recommended safe temperature for pork down to 145 F, the same as for other fresh meats. That means you don't have to cook pork well done any more, which is important if you're cooking a loin. With shoulder, it's a bit more complicated. You can treat it as an ordinary pork roast and eat it when its internal temperature reaches 145 F or 160 F, but its dense muscles and connective tissues will still be chewy. If you continue cooking until its temperature rises into the 180 F to 200 F range, the connective tissues will dissolve, the muscle fibers will soften, and your shoulder will develop its famously rich and lush texture.
You can cook your shoulder in several ways, but slow-roasting and old-school barbecue are two of the most common. In the oven, set the temperature to 250 F and let your roast cook undisturbed for six to eight hours, depending on its size, until it's fork-tender. If you want to crisp the skin -- a guilty pleasure -- remove the roast, raise the oven to 500 F, and return the roast to the oven for 15 minutes at the higher temperature. Barbecued shoulders are usually flavored with a dry spice rub, then cooked over charcoal and hardwood at 200 F to 250 F. This results in classic pulled pork, with a hard, smoky layer of "bark" on the outside and rich, moist pork inside.