Boil the brisket for 10 minutes, then rinse it under cold water and drain it well. Set aside.
Heat a large frying pan with 1 tablespoon oil over high heat. Stir-fry the spring onions and ginger until fragrant, 2-3 minutes. Add into the pressure cooker together with the brisket, Chinese marinade, water and sugar. Cook the brisket under high pressure for 7 minutes.
Release the pressure and transfer the beef brisket and sauce into a dish and allow to cool. Chill overnight, before slicing and serving.
Lee Kum Kee's Chinese marinade and rock sugar can be purchased in Chinese/Oriental speciality stores.
Alternative cooking methods
If you don't have a pressure cooker, you can simmer the brisket for 2 hours with an additional 250ml water.