Mexico City-Style Quesadillas with Cheese and Chile or Mushrooms - Rick Bayless

Ingredients

• 1 pound fresh-ground corn masa OR 1 1/4 cups powdered masa harina mixed with 1 cup plus 2 tablespoons hot tap water
• 2 tablespoons lard or vegetable shortening
• 1/4 cup flour (use 1/3 cup if working with powdered masa harina)
• A generous 1/2 teaspoon salt
• 1 scant teaspoon baking powder
• 10 ounces (2 1/2 cups) grated melting cheese like Monterey or a mild cheddar
• 1 large fresh poblano chile, roasted, peeled and cut into strips
• 12 ounces mushrooms (I prefer really full-flavored ones like shiitakes), rinsed or wiped clean
• 1 tablespoon lard or vegetable oil
• 1/2 medium white onion, finely chopped
• 2 fresh serrano chiles, (or 1 jalapeno), stemmed, seeded and finely chopped
• 1 1/2 tablespoons chopped fresh epazote, (optional)
• Vegetable oil to a depth of 1-inch