Cut the cauliflower into large 7.5cm (3-inch) florets. Bring a pot of water to the boil, add 1 tsp salt and the cauliflower. When it returns to the boil, cook for 1 minute, then drain.
Dry-roast the chickpea flour in a frying pan, stirring very often, until it has darkened by a couple of shades and smells roasted. Take it off the heat.
Place the cashews, garlic, ginger, oil and half the yogurt in a blender and blend until smooth. Stir in the remaining yogurt, spices, a little more salt and the chickpea flour. It should taste good, so adjust the salt if necessary. Place in a large bowl, add the cauliflower and leave for 20 minutes or so, if you have some time.
Preheat the oven to 200°C/400°F/gas mark 6. Line the base of the oven with foil, then oil an oven rack and place it in the middle of the oven. Once hot, place the cauliflower florets on the oiled rack and bake for 20–25 minutes, or until charred in areas and cooked through (the stalk should be tender when pierced with the point of a knife).
Meanwhile, mix together the coriander, tomatoes, chaat masala and chilli, then taste and adjust the seasoning. Spread the crème fraiche in a swirl over a serving platter. Spoon on just over half of the tomato mix. Place the cauliflower evenly over the crème fraîche, spoon over the rest of the tomato mix and serve.