Dip the matzas in a bowl of cold water for a minute. Wrap the matzas in a moistened kitchen towel and leave for 10-15 minutes.
Fry the onions in the oil until they are golden. Add the garlic and the meat and continue to cook until the meat is cooked through. Add the salt, pepper, cinnamon and allspice and remove the pan from the burner. Cool slightly, and add the eggs, mashed potatoes, walnuts and parsley. Mix well.
Preheat the oven to 180C (350F).
Grease a 24cm/12inch diameter round baking dish. Brush the wet matzas on both sides with a little olive oil and arrange 4 or 5 on the bottom, draping enough over the sides to later cover the filling. Spoon half of the meat mixture into the baking dish and flatten. Cover with a layer of matzas and top with the remaining half of the meat. Fold the matza draped over the side of the dish to cover the filling and brush with oil.
Place an additional matzo on top and brush with oil, too. Bake for 25-30 minutes or until golden brown. Remove from the oven, ladle the soup over the pie, and return to the oven for another 5 minutes. Cool slightly and invert on a plate before serving.