For the double crust leaf lard pastry: In a bowl, mix the flour and salt together with 2 knives. Cut in the lard until the mixture resembles coarse crumbs. Sprinkle the ice water over the mixture, a spoonful at a time, stirring with a fork and adding just enough water so it holds together. Shape into a ball, press into a flat disc, wrap in plastic wrap and chill for 1 hour.
For the pork filling: Heat a 10-inch cast-iron skillet over medium heat. Add the bacon and cook until crisp; remove to a plate. Add the pork and a pinch of salt and brown for 2 minutes; remove to a plate. Add the potatoes, celery, celery leaves, parsley, savory, garlic and onions and sweat for 3 to 5 minutes. Deglaze the skillet with 1 cup of water, scraping up the brown bits from the bottom with a wooden spoon. Add the pork and bacon back to the skillet with the cinnamon, cloves and a large pinch of salt, and simmer until the liquid has evaporated, 20 minutes. While the mixture is simmering, preheat the oven to 200°C. Lightly flour a work surface. Roll out the chilled pastry into two 13-inch rounds for a 10-inch double-crust pie, or into one 14-inch round for a single-crust pie. If using the double-crust method, line a 10-inch pie plate with one of the pastry rounds and fill with the meat mixture; cover with the remaining pastry. Trim and crimp the edges to seal, and cut small steam vents. Brush the top of the pastry with the egg yolk and milk mixture.
If using the single-crust method, place the meat mixture in a 10-inch pie plate and cover with the single pastry round. Trim, press the edges into the sides of the pan and cut small steam vents in the center. Brush the top of the pastry with the egg yolk and milk mixture. Bake until the crust is golden, 35 to 40 minutes. Let cool for 30 minutes and serve warm.