Combine all sauce ingredients in a medium pot. Simmer over medium heat until the peaches are very soft, about 20 minutes. Let cool slightly, then use an immersion blender to blend. Taste for seasoning and adjust as necessary.

Preheat oven to 300 degrees Fahrenheit (150 degrees Celsius). Lay meat on heavy-duty aluminum foil, then cover with one to two cups of the sauce. Seal the foil tightly, completely enclosing the meat and sauce. Place your foil-covered meat on a baking sheet, to catch any drips.

Bake for three and a half hours or until very tender. If desired, before serving, brush meat with some more sauce, then broil for five minutes to lacquer the meat.