To make the pie crust, mix the flour, eggs, salt, oil, and water in a bowl until the mixture holds together. Add more water or flour if necessary. Form into a ball, cover with wax paper, and refrigerate overnight.
Roll out the dough as thin as possible on a floured cutting board. You can use a large pie pan or small, individual pie pans. Place the dough into a greased pan, lay the bacon on top, and dust with the parsley.
In a separate bowl, beat the eggs and milk and pour over the dough and bacon, then season with sage, salt, and pepper. Cover with the remaining dough and press the edges with a fork.
Cut slits on the top to vent steam. Brush with the egg yolk and bake for 40 minutes.