First of all wash, scrub and peel the potatoes. Dice them finely. Rinse the diced potatoes twice or thrice to remove starch. Drain and set aside.
heat 2 tablespoons oil in a thick pan. Temper with mustard, urad dal and curry leaves. Saute well.
Add sliced onions and saute till they turn soft.
Add diced potatoes and saute well for 3-4 minutes.
Season with salt, chili powder and turmeric powder. Saute well for 3-4 minutes.
Cover and cook in medium flame for 10-12 minutes. Splash some water if needed to prevent sticking.
Once the potatoes turn golden and crispy, remove from flame. Serve with sambar rice.