Soak Poppy Seed or Posto in plain water for 30 minutes and then make a thick paste using Shil Nora or a food processor. I prefer to add 1 green chili while making the paste.Add little salt to the Poppy Seed paste.In case you are not available with a Shil Nora (shil batta) or food processor, you can use the dry jar of a mixer grinder to make a powder of Poppy seed and can add water after making the poder to make the paste.Wash Potatoes thoroughly and cut into small cubes and soak in water. Soaking potatoes it required else potatoes will turn dirty light brown in colour.Now heat the oil in a deep bottom pan and temper it with Onion Seed or Kalo jeera. Adding Kalo Jeera is completely optional but I love to add it.Add Potato cubes in the oil and start frying in medium flame for 3-4 minutes r till Potatoes soften a bit.Now add little salt and give it a mix and add slit green Chilies.Add 1 cup of water to cover the potatoes and cover the pan with a lid.Cook till potatoes soften completely and then add Poppy seed paste to the boiled potatoes and give Aloo Posto a careful mix.Cook till the raw smell of Poppy Seed paste gone completely and adjust water if required.Adjust gravy according to your preference. I prefer a medium thick Aloo Posto.