Blanch the pork in boiling water for 30 seconds and drain well. Coat the pork in cornflour and set aside.
In a small bowl, make the sauce by mixing together the soy sauce, sugar, vinegar, salt and Szechuan peppercorns. Set aside.
Heat oil in a wok over medium-high heat. Gently drop the pork into the oil, one piece at a time. Deep-fry each piece until lightly golden. Transfer the pork onto a plate.
Heat the oil in the wok to high. Add the pork back into the wok and deep-fry until golden brown. Remove from the wok and drain on a paper towel-lined plate.
Drain the oil from the wok, reserving about 2 tablespoons. Heat the oil until hot, add the ginger, garlic and spring onion and stir fry until aromatic.
Add the pork back into the wok and stir well. Pour the sauce into the wok and stir until the pork is coated evenly. Serve.