First, preheat the oven to 200°C (400°F/Gas 6). Melt the coconut oil in a large, deep tray on the stove over a high heat, then add the mustard seeds and fry for 1–2 minutes, or until they begin to pop.
If your stove isn’t gas, this can be done in a frying pan then transferred to the tray, or even done in the oven. Stir in the coconut milk, ginger, garlic, cumin, turmeric, salt, cauliflower and sweet potato.
Transfer to the oven and roast for 40 minutes, stirring halfway through.
To make the sambal, blitz together the coconut chips, coriander (stalks and leaves), chilli, lime zest and juice, and salt with a few splashes of water in a food processor, until you get a rough texture.
You can also do this by chopping and mixing everything by hand.
Remove the tray from the oven and set aside the cauliflower and sweet potato to make space for the spinach and chickpeas. Stir until the spinach is wilted, adding a splash of water if it’s a bit dry.
Heat the chapatis in a warm oven or, carefully using tongs, hold over the gas flame on your cooker for a few seconds.
To assemble: divide the curried chickpeas among four plates, top with the roasted cauliflower and sweet potato, then spoon over the sambal. Serve with the chapatis on the side for mopping up the spiced roasting juices.