Grind cumin seeds, red chilies, peppercorns, cardamon seeds, cinnamon, black mustard seeds and fenugreek seeds in a coffee or spice grinder. Put the ground spices in a small bowl. Add the vinegar, salt and brown sugar. Set aside.

Heat a tablespoon of oil in a wide pot over medium heat. Add the onions and fry, stirring frequently, until the onions turn brown and crisp, but be careful not to burn. Remove onions and place into an electric blender or food processor. Add 2 or 3 tablespoons of water and puree the onions. Add this puree to the ground spice mixture in the bowl. (This is the Vindaloo paste. It may be made ahead of time and frozen.)

Rinse blender or processor and add the ginger, garlic and 2 to 3 tablespoons water and blend until you have a smooth paste.

Add another tablespoon or two of oil to the pot that you cooked the onions in, and heat over medium-high heat. Cook the pork cubes a few at a time, browning lightly on all sides. Remove each batch with a slotted spoon and keep in a bowl. Repeat until all the pork has been browned, removing the last of the seared pork and setting it aside with the rest.

Now add the ginger-garlic paste into the same pot. Reduce to medium heat. Stir the paste for a few seconds. Add the coriander and turmeric. Stir for another few seconds. Add the pork cubes and any juice that has accumulated in the bowl, the vindaloo paste, and 1 cup water.

Bring to a boil, cover and simmer gently for 1 hour or until pork is tender. Stir occasionally through this cooking period, and set the lid ajar toward the end of the cooking time if you need to thicken the sauce and allow it to reduce.