Mix together the garlic, chilli, soy sauce, coriander and cumin seeds and vinegar in a small bowl and set aside.
Season the pork with salt and pepper.
Heat 2 tablespoons of the oil in a large frying pan and gently fry the potatoes, stirring frequently, for about 15 minutes until golden and tender. Lift out with a slotted spoon on to a plate.
Add another 2 tablespoons of the oil to the pan and fry the pork pieces, half at a time, for about 5 minutes, stirring frequently, until browned, lifting out with a slotted spoon on to the plate. Heat the remaining oil in the pan and gently fry the onions for about 10 minutes until softened and browned. Add the tomatoes, garlic mixture and measurement water and mix well.
Return the pork and potatoes to the pan and cook gently for 10 minutes until the pork is cooked through and tender and the tomatoes are pulpy. Stir in the chopped coriander and mint and check the seasoning, adding a little salt and pepper if necessary.