The first step is to boil the potatoes in water. Add 2 tsp of salt to the water while boiling. They need to be boiled till they are cooked but quite firm.
Make a paste of the tomato. In a bowl, whisk the yoghurt and add Kashmiri red chilli powder, turmeric powder and cumin powder. Mix them and keep this aside.
Once the potatoes are boiled, let them cool down. Discard the skin. If they are large-sized potatoes, cut them into quarters or halves, depending on the size.
In a kadai, heat mustard oil. Add bay leaf, dried red chillies. After that, add cinnamon, cardamom and cloves. Let them splutter in the oil for a few seconds. Now reduce the heat and add the cumin seeds. They burn fast, so keep the heat in check. As soon as you start getting the aroma of cumin, add heeng and then the ginger paste. Stir for a few seconds. Again, heeng burns fast.
At this point, add the tomato paste and increase the heat. Stir on high heat for a couple of minutes till the raw smell of the tomato is no longer there. Sprinkle water if you have to.
Then add the whisked yoghurt with the spices. Lower the heat so that the yoghurt doesn't split. Keep stirring continuously for a couple of minutes.
Then add potatoes to this. Give it a good mix. Add half a cup of warm water and salt. Then lower the heat and cover and let the potatoes cook in the spices and the yoghurt.
Check time and again to see how the potatoes and the spices are cooking.
Once the potatoes have become soft, and you need to break one and check if the potatoes have taken in the flavour or not.
Then, add sugar and a little more water. Potatoes soak up all the water. This doesn't have a runny gravy but a thick and saucy kind of gravy.
Add ghee, garam masala, split green chillies and adjust the seasoning. Keep stirring and mixing everything.
When you have the desired consistency, take it off the heat.
Serve with luchi or paratha or even radhaballavi.