Heat the oil in a large pan or wok. Add the lemon grass and red curry paste and stir-fry for 2–3 seconds. Add the onion and cook over a medium heat, stirring occasionally, for about 5–10 minutes, until the onion has softened but not browned.
Add the courgettes, cabbage, carrots and slices of broccoli stem. Using two spoons, toss the vegetables with the onion mi