1. Roast the chiles in a dry skillet set over medium-high heat for 20 seconds per side, or until they are pliable (careful not to burn). Use scissors to cut off the stem of each chile; then, cut open a slit in the side of each one. Remove the seeds and stems from the chiles and discard. Place the chiles in a large bowl; cover them with 3-4 cups of boiling water (you may have to place a heavy plate over them, to keep them submerged). Soak the chiles for 10 minutes (no longer than 20 or they will lose flavor); drain, reserving the soaking liquid. Transfer the chiles into a blender; add the garlic, onion, honey, lemon juice, oregano, rosemary, thyme, salt, pepper, and ⅓ cup of the reserved soaking liquid. Blend to the consistency of smooth paste (add a bit more of the liquid, if needed, to help the motor run). Add the grated chocolate and blend again, to combine.

2. Butter the bottom of a large, metal roasting pan. Pat-dry the pork well with paper towels. Using a large fork or paring knife, prick holes all over the pork (on both sides).Place the boneless leg of pork in the prepared pan. Pour half of the paste over one side of the pork, covering it fully; use your fingers to insert some of the paste into the holes. Turn the leg over in the pan and rub the remaining paste, so that all is covered. Tent aluminum foil over the pork, making sure not to let the foil touch the meat. Place the pork in the refrigerator and chill for at least 8 hours or up to 24 hours.

3. One hour before cooking the pork, remove it from the refrigerator and let it sit at room temperature. Preheat the oven to 400°F. Roast the pork, covered for 2- 2/12 hours or until the internal temperature reaches 155°F. Lower the heat of the oven to 350 degrees F; uncover the pork and roast, for another 30 minutes (or until it reaches 165°F and is browned slightly on top). Remove it from the heat and let it rest for 15 minutes before slicing thinly.

4. While it rests, strain the sauce through a sieve, pressing the solids against the sieve to remove all of the juices; then, discard the solids. Let the sauce sit for a couple of minutes; then remove the layer of fat that rises to the top and discard (you will have about 1 ¼ cup sauce; if you wish, you can thin it out with a bit of water). Transfer the sauce to a small pot and reheat over low heat; serve on the side or ladle it gingerly, over the sliced pork.