Whisk the flour and salt together in a large bowl. Remove ½ cup (125 mL) of the flour mixture and set aside.
With a pastry blender, cut the lard into the flour mixture in the first bowl until it looks crumbly and in pea-sized pieces.
Add the cold water to the reserved flour mixture and stir to form a paste.
Add the paste to the dry ingredients and toss with a fork. Use your hands to fully incorporate the paste, being careful not to overwork the dough.
Shape the dough into a flat disk, place in plastic wrap and chill for one hour.
In a large skillet, heat fat over medium heat; sauté onions and garlic until softened, about 5 minutes. Remove onion mixture and set aside.
Increase the heat to high. Cook the beef and pork, stirring to break up pieces and until no longer pink, about 5 minutes. Drain off liquid and separate the fat from the meat juices.
Add the onion mixture back into the pan with the meat. Add the savory, rosemary, sage, nutmeg, cinnamon, and cloves; cook over medium heat for 3 minutes. Add the red wine to the pan; reduce until it is a bit syrupy, about 5 minutes. Pour in stock and reserved meat juices, then bring to a boil; reduce heat to simmer. Add the chunks of celery, bay leaf, sprig of thyme, salt and pepper; then cook for 10 to 15 minutes or until most of the stock has been absorbed.
Remove the chunks of celery, bay leaf and the sprig of thyme.
Use a food processor to roughly chop the rolled oats.
Stir in the bread crumbs and chopped rolled oats to make a moist mixture. It should be very moist but not runny. If it is too stiff, add a bit of water. Taste and adjust the seasoning. Let cool completely. It is best if the filling can be refrigerated overnight as it will improve the flavours. (Filling can be frozen for up to two months.)
Preheat oven to 450ºF (230ºC).
Divide the chilled pastry in half. Roll the dough to ¼-inch (5 mm) thickness between two pieces of wax paper having lightly floured each side.
Line a deep dish 9-inch (23 cm) pie plate with pastry. Prick the bottom and the sides of the pastry with a fork. Chill for 20 minutes.
Warm the meat filling to about room temperature, just enough to add it easily to the dish. If it is too warm the bottom crust will not bake properly.
Using warm water, moisten the rim of the pie crust.
Roll out the second half of the dough and place over filling. Press the edges together. Trim and scallop the edge to seal.
Cut steam vents in the top crust. Decorate as desired.
Mix the egg and milk and brush over the surface of the pie.
Bake in a 450ºF (230ºC) oven for 10 minutes. Reduce the heat to 350ºF (180ºC). Bake until done, 40 to 50 minutes or until golden brown. Being a deep dish, it is important that it bakes through and the filling is piping hot.
Let cool for 10 minutes before cutting. Tourtière goes well with green tomato chutney and pickled beets.