Cut the pork into 2-3cm cubes. In a medium bowl, make the batter. Beat the egg white lightly with a fork until slightly frothy, then beat in the five-spice powder, cornflour, flour and a good grinding of pepper until thick and smooth. Stir in the pork so that each piece is evenly coated, then set aside.
Now make the sauce. In a small bowl, mix together the soy sauce, sesame oil, vinegar, sugar, tomato purée, cornflour blended with water, and the stock. Season with pepper and set aside. Blanch the carrot in a little boiling water for about 2 mins until tender but still crisp. Drain, then put under cold running water to stop the cooking. Drain again and set aside.
Pour the 1 tbsp rapeseed oil into a non-stick wok or large frying pan. When it’s very hot (test by dropping a piece of meat in – it should immediately sizzle), add the pork. Stir to separate all the pieces, then stir-fry for about 5 mins over a medium-high heat until the meat is no longer pink inside when cut, and the outside is golden and crispy. Remove with a slotted spoon and set aside.
Pour the remaining 2 tsp rapeseed oil into the wok and add the garlic, ginger, spring onions and pepper. Stir-fry for about 2 mins until starting to brown (still on quite a high heat). Pour in the sauce – it should immediately start to bubble rapidly – and stir in the carrot. As soon as the sauce has thickened slightly, about 30 secs-1 min, stir in the meat to quickly coat and heat through. Remove the pan from the heat, season with a pinch of salt and serve immediately, with the rice.