Heat 2 tablespoons of the oil in a heavy-based saucepan over a high heat for 1–2 minutes, then add the garlic and ginger and fry for 30 seconds before adding the onion and celery. Fry for 2–3 minutes, then add the minced beef and use a wooden spoon to break it up into small pieces. Cook for 6–8 minutes until the liquid has evaporated and the meat has browned, then add the stock, doubanjiang, light and dark soy sauce, oyster sauce, sugar and MSG (if using). Bring to the boil, then reduce the heat to low, cover and cook for 40 minutes, stirring occasionally.