How to Make It
In a food processor, combine the onion, ketchup, honey, vinegar, Worcestershire sauce, chile powder, garlic and 2 tablespoons each of salt and pepper and pulse until smooth. Transfer the paste to a large resealable plastic bag. Add the pork roast, turning to coat it with the paste; seal the bag and refrigerate for at least 8 hours or overnight.
Preheat the oven to 325°. Set the pork in an enameled casserole and cover with the paste. Add 1 cup of water and bring to a simmer. Cover the casserole and roast the meat in the oven for 3 1/2 hours, or until meltingly tender; turn the roast occasionally and add more water if it is looking dry. Transfer the pork to a cutting board and let cool. Remove the strings and pull the meat into thick shreds. Transfer to a bowl and toss with 1/2 cup of the Espresso Barbecue Sauce.
Put the masa harina in a large bowl. Add 1 1/2 cups of hot water in a thin stream and beat at low speed until a dough forms. Beat at medium-low speed until the dough is cool, about 5 minutes. Add the shortening, 1 tablespoon at a time, beating well after each addition. Beat in the baking powder and 2 teaspoons of salt. Scrape the dough into a large bowl and fold in 2 1/2 cups of the shredded pork.
Arrange the corn husks on a large work surface. Scoop about 1/4 cup of the tamale filling into the center of each husk. Fold the ends of the husks over the filling, then roll the husks up to enclose the filling completely. Alternatively, wrap 1/4 cup of tamale filling in a rectangle of foil, forming an oval shape, and twist the ends securely. Place the tamales, seam-side down, in a large steamer basket, in several layers if necessary.
Steam the tamales until the filling is firm, about 20 minutes. Serve the tamales piping hot, with the remaining barbecue sauce on the side.
Masa harina, a flour made from corn that has been treated with lime, is used to make tortillas and tamales. It is available at most supermarkets.