Firstly, wash and peel the potatoes. Cut into cubes.
Soak the poppy seeds in warm water for 30 minutes. Drain and grind posto to a smooth paste (posto bata), using little water and keep aside. For a spicier dish, you can add 1-2 green chillies and grind along with poppy seeds.
Heat 1 tbsp of oil in a pan. Add kala jeera and let it splutter.
Add the green chillies and potato cubes. Sauté for 1-2 minutes.
Add salt, turmeric, sugar and sufficient water. Cover and cook till the potatoes are 3/4th done.
Add the poppy-seeds paste and simmer till the potatoes are cooked through and all the water evaporates.
Finally, drizzle one tablespoon of mustard oil on top, blend well and remove.
Serve Bengali Aloo Posto with Rice and kolai-er dal