To prepare the marinade: Blend together the tamarind paste, if using, orange juice, molasses, chile powder, vinegar, oil, and basil. Pour the marinade over the pork loin in a shallow glass baking dish, cover, and marinate overnight in the refrigerator.
To prepare the stuffing: Place the figs, garlic, and pureed chipotles in a food processor and pulse until semi-smooth. Transfer to a bowl and fold in the remaining ingredients.
To prepare the pork: Remove the pork from the marinade, reserving the marinade, and blot dry. Butterfly the loin lengthwise, leaving 1/2 inch of meat attached to connect the 2 halves of the loin. Open the pork loin and cover it with plastic wrap. Pound lightly with a butcher's mallet or heavy pan to an even thickness, 1/2 to 3/4 inch. Mound the stuffing down the center of the loin and fold it closed. Tie the loin carefully at 1-inch intervals with butcher's string. The loin may be prepared to this point up to 24 hours in advance.
Preheat the oven to 325 degrees. Pour the marinade into a saucepan and reduce it over low heat to a glazelike consistency. Heat the olive oil in a saute pan over moderate heat and sear the meat. Transfer to a metal rack wet in a roasting pan and roast for 40 to 50 minutes, or until the internal temperature is 145 degrees. Bursh the pork liberally with the glaze during the last 5 minutes of cooking. Let the meat rest for 5 minutes or so before removing the twine. Slice and serve.
Serving Suggestion: Serve with sauteed chanterelle mushrooms with apple wedges.