Peel and thinly slice the onions. Pull any tatty leaves off the cauliflower and discard. Chop any remaining leaves and add them to the onions. Chop the cauliflower into bite-sized chunks.
Warm a large pan on a medium heat for 1 min then pour in 2 tbsp oil. Add the onions and the chopped cauliflower leaves and season with a pinch of salt. Fry, stirring often, for 6 mins till softened.
While the onions cook, peel the potatoes and chop them into 1-2cm chunks. Scrub and trim the carrots, then chop into 1cm-thick slices. Fill and boil your kettle. Drain and rinse the chickpeas.
When the onions have cooked for 6 mins, tip in ½-1 tbsp madras spice blend (use more or less, depending on how hot you prefer your curry). Stir for 30 secs, then pour in the coconut milk and 300ml hot water. Bring up to a bubble, then add the cauliflower, potatoes and carrots to the pan. Tip in the chickpeas, pop a lid on the pan and simmer for 15 mins, stirring occasionally.
While the curry simmers, finely shred the kale leaves, discarding the woody cores. After 15 mins, the potatoes and cauliflower should feel almost tender when pierced with a knife. Add the kale and stir in. Cook for 4 mins, without the lid, to wilt the kale.
Taste the curry and add more salt or a little pepper if you think it needs it. Serve in warm bowls.