Heat the oil in a large frying pan over a medium heat. When hot, add the onion and stir-fry for 2–3 minutes. Add the garlic and ginger and stir-fry for another minute, until aromatic.
Add the beef, turn up the heat a little and stir-fry for a minute or two until beginning to colour. Add the gochujang paste, doenjang paste, some salt and a few grindings of pepper. Stir to combine together and stir-fry over a high heat for 1–2 minutes, breaking up the beef until almost cooked.
Add the stock, mirin, soju (or sake), soy sauce, sugar, cornflour mixture, sesame oil and tofu and gently mix together. Bring to the boil, then reduce the heat and simmer gently for 15–20 minutes. Stir frequently and cook until the sauce has reduced down and is thick and glossy.
Serve in bowls with the spring onions, sesame seeds and coriander leaves scattered over and the rice on the side.