Grind cumin seeds, red chilies, peppercorns, cardamom seeds, cinnamon, black mustard seeds and fenugreek seeds in a coffee-grinder or other spice grinder. Put the ground spices in a bowl. Add the vinegar, salt and sugar. Mix and set aside. Heat the oil in a wide, heavy pot over a medium flame. Put in the onions. Fry, stirring frequently, until the onions turn brown and crisp. Remove the onions with a slotted spoon and put them into the container of an electric blender or food processor. (Turn off the heat.) Add 2-3 tablespoons of water to the blender and puree the onions. Add this puree to the ground spices in the bowl. (This is the vindaloo paste. It may be made ahead of time and frozen.) Dry off the meat cubes with a paper towel and remove large pieces of fat, if any. Put the ginger and garlic into the container of an electric blender or food processor. Add 2-3 tablespoons of water and blend until you have a smooth paste. Heat the oil remaining in the pot once again over a medium-high flame. When hot, put in the pork cubes, a few at a time, and brown them lightly on all sides. Remove each batch with a slotted spoon and keep in a bowl. Do all the pork this way. Now put the ginger-garlic paste into the same pot. Turn down the heat to medium. Stir the paste for a few seconds. Add the coriander and turmeric. Stir for another few seconds. Add the meat, any juices that may have accumulated as well as the vindaloo paste and the water. Bring to a boil. Cover and simmer gently for an hour or until port is tender. Stir a few times during this cooking period. Serve with rice.