Rinse sabudana 2–3 times until the water runs mostly clear. Drain well, then add enough water to just cover the pearls. Soak for 4–6 hours, or until soft and easily pressed between your fingers.
Roast and Crush the Peanuts. Dry-roast the peanuts in a pan over medium heat until fragrant. Let them cool and crush them coarsely. Keep some texture; don't make a fine powder.
Boil the potatoes until tender. Peel them and cut into small cubes.
Heat ghee in a heavy-bottomed kadai over medium heat. Add cumin seeds and let them sizzle. Add curry leaves and slit green chilies.
Add the cubed potatoes and sauté for 2–3 minutes until they are lightly golden around the edges.
Reduce the heat to low. Add the soaked and well-drained sabudana, crushed peanuts, sendha namak, and sugar. Gently fold everything together, cover, and cook for 4–5 minutes until the sabudana becomes glossy and translucent.
Turn off the heat and gently mix in lemon juice and chopped coriander. Let the khichdi rest for 2–3 minutes, then serve hot with yogurt.