Put the vegetable oil in a large non-stick frying pan set over a medium heat. When hot, add the mustard seeds and fry until they fizz and pop. Add the garlic and ginger and continue to fry for 30 seconds, taking care not to burn the garlic.
Add the white cabbage, ground turmeric, chilli powder, salt, sugar and English mustard and mix well, then cover with a lid and cook, stirring occasionally, for 25–30 minutes or until the cabbage is cooked through and tender.
Finish by stirring through the fresh lemon juice just before serving.