The cut of pork determines if it needs to be parboiled and for how long. For example, pork belly — the fatty, umami-rich cut used in twice-cooked pork — needs parboiling before frying to firm the meat and render some of the fat. Pork stomach, on the other hand, needs parboiling for a couple hours to remove its feral taste and aroma. Parboiling isn’t meant to break down connective tissue to tenderize tough cuts, such as ribs or shoulder; connective tissue renders at about 160 degrees Fahrenheit, and parboiling requires a water temperature of about 180 F.
Trim the pork of any fat hanging off the meat or any that pulls off easily by hand. Let the pork come to room temperature on a plate lined with paper towels.
Bring a pot of water to a boil. Add the pork to the boiling water and skim the surface of froth and scum as needed throughout parboiling.
Adjust the water temperature until to a simmer, or about 180 F. Simmer the pork until cooked through, about 20 to 25 minutes per pound.
Transfer the pork to a colander or sink, and run cold water over it for about 10 to 15 minutes per pound. Slice the pork belly into slices 1/4 to 1/3 inch thick for frying.
Rinse the tongue, liver, intestines or other offal cut under cool running water until it runs clear and most of the gamey, feral smell diminishes, about 15 minutes.
If you are parboiling tripe, scrub it in a mixture of equal parts white distilled vinegar and water for 15 minutes.
Bring a pot of water to a boil. Add the offal to the boiling water, and skim the surface of scum and froth as needed throughout parboiling.
Parboil the offal until tender, about 1 to 2 hours, depending on the cut. Tongue, heart and tripe take as long as 2 hours, whereas liver takes about 1 hour.
Drain the offal in a colander and rinse it under cold running water until cool. Slice the offal and saute, braise or cook it as desired to finish.
References and ResourcesScience of Cooking: Science of Slow Cooking
Serious Eats: Chichi's Chinese: Twice-Cooked Pork