Soak the chilis and poppy seeds, in water, for at least 30 minutes thereafter strain and grind to a smooth paste, using 2-3 tablespoons of water. Keep it aside
Heat the oil, over medium flame until it smokes. Add the dried chili and paanch phoron. Once the mustard seeds in it crackle, add the potatoes, turmeric and salt
Stir fry these until the potatoes get a light brown colour on them
Add in ½ cup of hot water, cover and cook the potatoes on a medium flame until 90% cooked
Next add the poppy seeds paste along with 2-3 slit chilis (optional) and mix in gently. Reduce the heat to medium-low, cover and cook
Once the potatoes are cooked completely switch the flame off and drizzle a spoon of mustard oil
Serve your yummy Bengali aloo posto with a bowl of steamed rice and dal. Enjoy!