To make dough: In a large bowl combine flour, salt, lard, and butter. Mix lightly with your fingers until the dough forms pea-sized pieces. Stir in iced water and lightly knead until dough forms a ball. Wrap in plastic wrap and refrigerate for 1-2 hours or overnight.
To make filling: Heat olive oil in a frying pan and add diced onion, salt and pepper. Cook over moderate heat until onions are soft and begin to turn lightly golden. Add chard stems and cook a minute or two then add the chard leaves and cook until tender, about 3-4 minutes. Remove from heat and cool. Mix cooled cooked chard with grated cheeses and taste, adjust seasoning.:
To assemble empanadas: On a lightly floured board, roll the dough out to 1/8 inch thickness and cut 6 circles about 5 inches each or 12 smaller circles. Place filling onto half of circle of dough leaving a border and wet the edges of the dough with the egg wash, then fold the dough over to enclose the filling. Seal the edges by pressing the top to the bottom with the tines of a fork. Chill at least 30 minutes before baking.
Preheat oven to 350 degrees. Place empanadas on a baking sheet and brush tops with egg wash and sprinkle with freshly cracked pepper. With a sharp knife, cut small slits in the top of each empanada to allow steam to escape. Bake 30 minutes or until dough is golden. Transfer to a cooling rack to cool slightly. Serve warm or at room temperature.
c.1997, M.S. Milliken & S. Feniger, all rights reserved