Line a 6-quart Crock-Pot Brand(R) slow cooker with the banana leaves. Put one across it the long way and one sideways.
Sprinkle the pork generously with salt and fresh ground pepper. Place the pork shoulder in the slow cooker on top of the banana leaves.
Combine the ancho chile paste in a bowl with 1/2 cup of the lime juice and 1 teaspoon salt. Stir until well blended. Pour the ancho chile mixture over the top of the pork along with the chicken broth. Scatter the white onion on top of the pork. Wrap the banana leaves over the top of the pork to seal it off, and put the lid on the slow cooker. Cook on LOW for 8 to 10 hours.
While the meat is cooking, soak the red onions in 1/2 cup of the lime juice. The resulting pickled red onions are somewhat sweet and completely fantastic.
When it is nearly time to eat, prepare the rice according to package instructions. Mix in the remaining 1 tablespoon lime juice, the cilantro and some salt. Add some butter, if using. (Measurements on this will vary depending on taste.)
When the pork is finished cooking, remove from the slow cooker and let it rest uncovered for 15 minutes. Skim off any excess fat from the liquid in the slow cooker. Using 2 forks, pull the pork so that it shreds away from the bone and shred into bite-size pieces. Season the liquid from the slow cooker with additional salt.
To build the tacos, add the meat, some cooking liquid, rice, pickled red onions and the other taco fixings to the tortillas.
A viewer or guest of the show, who may not be a professional cook, provided this recipe. It has not been tested for home use.