Rinse 1½ cups poha in a strainer under running water until the flakes turn soft; a flake should break cleanly when pressed between thumb and finger. Drain completely and set aside to rest while you cook the tempering.
Heat 1 tablespoon oil in a kadai over medium heat. Add ½ teaspoon mustard seeds and let them pop.
Add 1½ tablespoons raw peanuts and sauté 1 to 2 minutes until they start turning brown.
Add the chopped red onion, green chili, and 10 to 12 curry leaves. Cook about 2 minutes until the onions soften.
Add ⅓ cup soaked green peas and ½ cup potato cubes, mix, then cover and cook 4 to 5 minutes until the potato is tender.
Stir in the turmeric and salt. Add the rinsed poha and toss gently to combine; if it feels dry, sprinkle 1 to 2 tablespoons water over the top. Cover and steam on the lowest heat 1 to 2 minutes.
Turn off the heat. Stir in the chopped cilantro and the juice of ½ lemon. Garnish with sev and more cilantro, and serve hot.