Melt butter in a large frypan or casserole with a lid. Add onion, garlic, ginger and spices, cook 1-2 minutes until fragrant and onions are golden.
Add potatoes, 1 cup water and season to taste, stir to coat, cover and simmer for 10 minutes. Remove the lid and stir in cauliflower and chilli, cook for a further 10 minutes, until cauliflower and potatoes are tender and glossy. There should only be just enough liquid to moisten the vegetables.
To serve, spoon onto a serving platter, scatter with coriander and drizzle with yogurt.
- If you like a little more spice, add a teaspoon of garam masala or some bruised cardamom pods to this dish.