Cut chicken, beef and pork into 1 inch cubes and place in a large bowl. Combine with onions; cover and refrigerate for at least 12 hours.
In a small bowl mix together the salt, pepper, cloves, nutmeg, cinnamon and allspice.
Roll out 2 pie crusts making them slightly thicker than for a normal pie.
Arrange the salt pork evenly in the bottom of a 3 quart casserole. Layer with 1/3 of the marinaded meat mixture and 1/3 of the potatoes. Sprinkle with 1/3 of the seasoning mixture. Cover with one pie crust cutting a small hole in the centre. Repeat with 2 more layers of meat, potatoes and seasoning mixture. Cover with remaining pie crust and cut a small hole in the centre.
Slowly add enough chicken stock through the hole in the crust until liquid appears. Cover the dish and bake in a preheated 400°F oven for 45 minutes or until liquid simmers.
Reduce the temperature to 250°F and continue to bake, covered, for 5 to 6 hours more or until top crust is a rich golden brown.