Peel and dice potatoes into medium cubes.
Heat vegetable oil in a pan, crackle mustard seeds and sesame seeds.
Add ginger paste and chopped green chili; sauté for 30 seconds.
Add diced potatoes, turmeric powder, coriander powder, sugar, salt, and water.
Cover tightly and simmer on low heat for 15 minutes until potatoes are soft; stir in fresh lemon juice before serving.