1. Peel and thinly slice the onions. Trim the base off the cauliflower, removing the leaves, then slice the cauliflower into small florets. Cut the stalk into bite-sized pieces. Peel and chop the potatoes into small 1-2cm-thick pieces. Peel and finely chop the garlic and ginger. Thinly slice the chilli. Finely chop the coriander leaves and stalks.
2. Spoon 2 tbsp ghee into a large frying pan and warm over a medium heat. Slide in the onions and add a good pinch of salt and pepper. Fry the onions for 10-15 mins, stirring occasionally, till softened and golden. Add the chopped cauliflower and potatoes to the pan, along with the garlic, ginger and chilli. Add 1 tsp ground coriander, 1 tsp ground cumin, 1 tsp ground turmeric and 1 tbsp garam masala. Cook for 2-3 mins, stirring frequently, till the pan smells aromatic.
3. Pour in 300ml water and bring to a simmer. Simmer the vegetables for 20 mins, till the potatoes and cauliflower are tender and the sauce has reduced and thickened. When the veg are cooked, remove the pan from the heat. Stir in 4 tbsp yogurt, the juice of 1 lemon and most of the chopped coriander. Pop the pan to one side.
4. While the veg cook, tip the rice into a separate large pan. Add 4 cloves, 4 cardamom pods and 1 cinnamon stick. Grate in ½ nutmeg and season with a good pinch of salt. Pour in 600ml cold water, set on a high heat and bring to the boil. Once boiling, turn the heat down to a simmer and cook for 5 mins, till the rice is part-cooked but still has a little bite. Drain the rice over a bowl, reserving 6 tbsp of water. Fish out and discard the cloves, cardamom and cinnamon.
5. Warm your oven to 200°C/ Fan 180°C/ Gas 6. Melt the remaining turmeric ghee in a small pan. Spoon half of the potato and cauliflower mixture into a large ovenproof pan. Top with half of the rice, and use the back of a spoon to flatten it. Spoon over half of the melted ghee and half of the reserved rice cooking water. Repeat the layering of the veg and rice, then top with the remaining ghee and water.
6. Tip the wholemeal flour into a large bowl and slowly mix in 200ml cold water. Knead the mixture together till it forms a smooth dough, adding a little more water if needed to bring it together. Roll the dough out into a circle a little larger than the circumference of the pan. Lay the dough over the pan and press at the edges to seal. Slide the pan into the hot oven and bake for 30 mins, till the dough is golden on top.
7. To serve, cut open the dough lid and discard it. Spoon the rice and veg onto warm plates. Serve with the remaining yogurt, garnished with the remaining coriander.