1. The cornhusks. Bring the cornhusks to a boil in water to cover in a large saucepan then weight with a plate to keep them submerged and let stand an hour or so. 2. The batter. With an electric mixer, beat the chilled lard or shortening with the baking powder until light in texture, about 1 minute. Continue beating as you add the masa (fresh or reconstituted) in three additions. Slowly pour in a generous 1/2 cup of the broth, beating all the while. Continue beating for another minute or so, until a 1/2-teaspoon dollop of the batter floats in a cup of cold water (if it floats you can be sure the tamales will be tender and light). Beat in enough additional broth to give the mixture the consistency of soft (not runny) cake batter (it should softly hold its shape in a spoon). Season with salt (yes, it will involve tasting a little raw batter), usually about 1 scant teaspoon, depending on the saltiness of the broth. For the lightest textured tamales, refrigerate the batter for an hour or so, then rebeat, adding enough additional liquid to bring the mixture to the consistency it had before. (You may find it necessary to add a little salt, too.) 3. The filling. Roast the tomatoes on a baking sheet set 4 inches below a very hot broiler until blackened and blistered on one side, about 6 minutes; flip and roast the other side. Peel and roughly chop, collecting all the juices with the tomatoes. Roast the chiles directly over a gas flame or 4 inches below the very hot broiler until blackened on all sides, about 5 minutes for open flame, about 10 minutes for broiler. Cover with a kitchen towel and let stand 5 minutes. Peel, pull out the stem and seed pod, then rinse briefly to remove bits of skin and seeds. Slice into 1/4-inch strips. In a large (10- to 12-inch) skillet, heat the oil over medium-high, then add the onion and cook, stirring regularly, until nicely browned but still a little crunchy, about 5 minutes. Add the garlic and herbs, toss a minute longer, then stir in the chiles, tomatoes and mushrooms. Cook, stirring regularly, until everything is reduced to a thick mixture that easily holds it shape in a spoon, about 5 minutes. Season with salt, usually about 1 teaspoon, and cool to room temperature. 4. Forming and steaming the tamales. Pick out 16 of the nicest cornhusks for forming the tamales, then use about 2/3 of the remainder to line a steamer (youll need one that's at least 4 inches deep--a Mexican tamal steamer is traditional, though a vegetable steamer in a deep pot will do here, or a Chinese steamer works well, too). Tear 16 long, 1/4-inch-wide strips from the unused cornhusks for tying the tamales. One by one form the tamales: lay one of the good cornhusks in front of you, lightly dry it, then spread about a scant 1/4 cup of the batter into a 4-inch square, leaving at least a 1 1/2-inch border on the pointy end of the husk, a 3/4-inch border along the other sides. Spoon a good 2 tablespoons of the filling down the center of the batter. Pick up the two long sides of the husk and bring them together (this will cause the batter to roll around the filling, enclosing it). Roll the flaps of the husk in the same direction around the tamal. (If the husk is so small that the tamal doesnt seem very well wrapped, roll it in another husk.) Fold up the empty, pointy 1 1/2-inch section to close off the bottom, then secure it by loosely tying one of the strips of husk around the tamal and folded flap. Stand the tamal on the folded end in the steamer (the top of the tamal will be open). Continue spreading, filling, rolling and folding until all the tamales are made (you may have a little filling left, which is great in scrambled eggs or soft tacos). Fill in any gaps in the steamer with loosely wadded foil, to keep the tamales from sliding down as they steam. Lay any unused husks over the tamales, then bring a couple of inches of water in the steamer to a boil. Cover the pot tightly and steam over medium heat for 1 to 1 1/4 hours (ones made from reconstituted masa will take a little longer than those made from fresh); make sure that the water stays at a good steady boil and never runs out--otherwise your tamales won't be as light. If the water runs low, pour a little boiling water into the steamer, being careful not to pour it onto the tamales. The tamales are done when the husk peels away easily. Let them firm up a few minutes in the steamer, off the heat, before setting your fragrant creations before your guests. Yield: 4 1/2 cups 16 tamales