Combine all the ingredients in a saucepan and add water to cover. Turn the heat to high, bring to a boil, and skim any foam that comes to the surface. Partially cover, and adjust the heat so the mixture simmers steadily. Cook until the meat is very tender, about 30 minutes. Remove from the liquid and cool.

Shred the meat with your fingers. Taste and adjust seasonings; use as taco filling within a couple of days.