Peel the Boiled Potatoes. Cut them lengthwise and then into 1 inch thick squares. Keep them aside.
Finely chop the tomatoes and keep them aside.
Now place a heavy bottom pot on the stove on medium flame.
Add oil to the pot and let it heat up.
Once hot, add mustard seeds. Once the mustard seeds start to crackle, add the cumin seeds. Let them splutter.
To this add the finely chopped tomatoes, along with turmeric, red chili powder, coriander powder and salt. Sauté until the tomatoes are mushy and spices are cooked. It should take about 3-4 minutes.
Now add 3 cups of hot water, and bring it to a simmer.
Once the curry starts to simmer, mash 6-7 dices of potatoes and add to the curry. Mashing a few diced potatoes will help thicken the curry sauce.
Now add the diced potatoes and sugar. Mix well.
Simmer the potato curry until the water reduces to half and the curry thickens. This step should take about 5-7 minutes.
If the curry becomes thicker than you want, simply add some more water.
Once the curry is ready, garnish with fresh roughly chopped cilantro.
Serve it with rotis, rice, curd rice, khichdi, or lentils.