In a bowl, mix the masa with the lard, flour, salt and baking powder. Add a little water if needed until the dough is soft and sticks lightly to your hands. Divide into 12 balls and cover with plastic wrap.
Divide the cheese into 12 portions, pressing each one into a flat oval. Using a tortilla press (or 2 plates) flatten a ball of the dough between 2 sheets of plastic to make a medium-large (4 to 5-inch) thickish tortilla. Remove the top piece of plastic and lay a portion of the cheese across half of the uncovered tortilla, leaving a ½-inch border at the edge. Top with a leaf of epazote (or 2 leaves of cilantro). Slip you hand under the plastic beneath the uncovered side of the tortilla, then carefully fold the tortilla over the filling. Press the edges together to seal. Peel the plastic off the quesadilla and lay on a tray covered with plastic wrap. Continue making masa balls into turnovers and cover with plastic wrap.
Heat the oil until hot enough to make the tip of one of the turnovers sizzle sharply. Fry the turnovers 2 at a time until golden brown, about 2 minutes per side. Drain on paper towels and keep warm in a low oven until you are ready to serve. These are delicious with Tomatillo-Avocado Salsa