Cut the potato and brinjal into medium sized cubes. Slit the green chillies in half. Cut the tomato into large cubes.
Heat oil in a kadai. Add mustard seeds and cumin seeds and let them splutter.
Add the potato, brinjal and green chillies. Mix well.
Add turmeric powder, red chilli powder and salt. Add the tomato and mix well. Add 2 cups of water and cook keeping the lid closed for 15 minutes on a medium flame.
Now add the coriander powder and cook for another 5 minutes.
Once the potatoes are well cooked, add the sugar and cook on high flame for 2 minutes. Turn off the stove and garnish with fresh coriander. Enjoy with ghee roti or plain rice.