Mix the sugar, salt, soy sauce, coriander, cumin, chili powder, turmeric and cornflour paste in a bowl, adding a little water if necessary. Add the diced pork, mix thoroughly and refrigerate for about an hour.
Heat some of the oil in a wok and stir fry the onions and garlic for around 3 minutes. Then add the pork together the marinade and stir fry for a further 4 or 5 minutes or until the pork is cooked. Remove the pork/onions and keep aside.
Add a little more oil to the wok and stir fry the diced potatoes until brown on all sides. Add around 300 ml of warm water, cover the wok and simmer for about 10 minutes or until the potatoes are cooked through.
Return the pork and onions to the wok, mix thoroughly and bring to the boil. Mix in the garam masala and simmer for 1 minute. Serve hot with naan bread or roti and/or rice.