Slow-Cooked Lamb or Beef Barbacoa tacos - Rick Bayless

Ingredients

• A 12-inch chunk of agave leaf (penca de maguey) OR a dozen or so good-size avocado leaves (available at Mexican groceries) OR a 2-foot piece of banana leaf
• 2 to 3 tablespoons vegetable oil or fresh-rendered pork lard
• Salt
• 2 dried guajillo chiles, stemmed, seeded and torn into large pieces
• 2 dried ancho chiles, stemmed seeded and torn into large pieces
• 4 garlic cloves, peeled
• 2 tablespoons vinegar (plus more if you think the marinade needs it)
• 1 teaspoon salt
• 1 canned chipotle chile en adobo
• 1/2 teaspoon fresh black pepper
• 1/2 teaspoon dried Mexican oregano
• 1/2 teaspoon fresh allspice or cinnamon (preferably Mexican canela)
• About 1/2 of a 12-ounce bottle of beer (Modelo Negra is a good—but completely optional)
• 20 warm corn tortillas
• 1 cup roasted tomatillo salsa, chipotle salsa and/or Mexican hot sauce
• 3-4 limes, cut into wedges