preheat oven to 350.

In a bowl, combine pork, veal or beef, salt, and generous grindings of pepper, cinnamon, cloves, allspice, sage, mustard, and vinegar, if using.

Heat a large skillet over high heat. Lower heat to medium-high and add meat mixture. Cook the meat, chopping through it and stirring to break up any clumps, until it is brown; don not overcook.

Push meat to one side of skillet. Add onions to other side. Cook until onions are softened, not browned.

Transfer mixture to a large bowl. Add mashed potatoes and work them in thoroughly, break up any lumps of meat or potato.

Place filling in the bottom crust, mounding it well. Top with other crust; crimp to seal them together. Brush with the beaten egg mixture. Cut several steam vents in top of pie. Put pie on rimmed baking sheet.

Bake pie for 1 hour or until crust is golden brown.