Make the marinade by mixing together the sugar, salt, soy sauce and cornflour slurry. Mix in the pork, let marinate for 15 minutes.
Heat a large frying pan with oil over medium heat. Add the pine nuts and fry until golden brown. Remove from the pan and set aside, keep the oil in the pan.
Turn the heat to high. Stir-fry the garlic until aromatic, 2-3 minutes. Add the pork and stir-fry until cooked through, about 4-6 minutes. Set aside, leaving any oil that's left in the pan.
Over high heat, fry the onions with some salt until soft, about 2-3 minutes. Add the cooked pork and green pepper. Stir for 1-2 minutes before adding the hoisin sauce, oyster sauce and water. Stir until well combined. Toss with pine nuts and serve.