In a bowl, mix together the oregano, salt and black pepper. Use to season the pork. Let sit for 10 minutes.
Coat the pork in cornflour, then dip in beaten egg and coat in breadcrumbs. Chill the pork for 10 minutes.
Meanwhile, mix together the HP sauce, tomato sauce, sugar, water and Worcestershire sauce, set aside.
Heat a frying pan with 1/2 cup (125ml) oil over medium heat. Fry the pork until light brown, 3-5 minutes. Transfer to a dish. Turn the heat to high and fry the pork for the second time, until golden, 2-3 minutes. Drain on a paper towel-lined plate.
Leave a little amount of oil in the pan. Stir fry the onion with salt until soft, 3-4 minutes. Stir in the sauce and heat through, 1-2 minutes. Pour over the pork pieces or serve on the side.