First put the bones to boil in 1 quart (9 dl) of water with the onions, the whole sage leaf, the bay leaf, a sprig or two of marjoram, some sprigs of thyme, salt and pepper. Boil for 2 hours, to reduce the stock to little more than 2½ cups (6 dl) of liquid, then cool and skim off all fat. Taste the stock and check seasoning. It should have begun to jell as it cools.
While the stock is boiling, prepare the filling. Cut the pork in dice approximately ¼ inch (0.5 cm) square (kitchen scissors are easier to use than a knife) but do not mince. Fat may be included, but not skin or gristle. Mix together the pork, 1 teaspoon of salt, ½ teaspoon of pepper and the finely chopped sage leaf.
Prepare the crust by sifting together the flour and ½ teaspoon of salt. Rub 4 tablespoons (60 g) of the fat into the mixture with the fingertips. Put the rest of the fat on to boil with the milk and water. Make a well in the flour and when the liquid is boiling, pour it in and stir with a wooden spoon. Knead well and let the pastry stand for 10 minutes.
The raising of the pie may be done in several ways, but this is probably the easiest. Take a round casserole or cake tin the size of the pie you want to make. It must have straight sides and be of sufficient height. Roll out the pastry into a large, roughly circular piece about ½ to ¾ inch (1 to 2 cm) thick. Stand the round pot or cake tin, open end up, in the middle of the pastry and work it up to cover the sides of the pot. Turn the pastry-covered pot on its side and roll it a few times to smooth the outside and loosen the pot. Gently work the pot out; the pie case should remain standing.
Fill the pie case at once by packing the pork mixture closely down into it to within ¼ inch (0.5 cm) of the top. Put in 2 tablespoons of cold water and dot the top of the meat with the butter. Trim the top of the pie with a sharp knife, roll out the trimmings, and cut out a lid that is larger than the top of the pie case. Dampen the top edges of the pie case with a little milk, press on the lid and firmly crimp the edges all round to make a raised ridge. The top of the pie can be left plain with 2 or 3 slits or a round hole neatly cut in the middle, or it may be decorated with leaves and a rose.
If you want to raise the pie without using a pot, cut a round for the bottom which is ½ inch (l cm) bigger in diameter than you think you require. Roll your paste into long thin snakes, as children do with plasticine or as a potter does with clay for certain pots. Coil the snakes round the edges of the bottom, one on another, until you have walls of the required height. Then carefully work them as smooth as possible outside and in with your fingers, always working the paste upwards. Fill the pie and put on the lid as described above.
Brush the pie all over with the beaten egg. Bake at 375°F (190°C, Gas Mark 5) for 20 minutes to set the pastry; then reduce the temperature to 325°F (170°C, Gas Mark 3). Put the pie lower in the oven, cover the top lightly with foil and bake for a further 1¾ hours.
Remove the pie from the oven about 10 minutes before the end of the cooking time, brush over with the remaining beaten egg and return to the oven.
Lastly, reheat the jellied stock. As soon as the pie comes out of the oven, slowly pour the stock through the hole in the top of the crust until it fills the pie.
Leave the pie to become quite cold before serving.