Cut the potatoes in medium size. Keep this aside.
Preparation of coconut milk
Transfer the grated coconut into mixer grinder and grind it for 1 min. Sprinkle little bit of hot water to get that thick gravy. Keep this aside. Now add more water into the grated coconut and grind it for 2-3 mins. Prepare one cup of coconut milk from that.
Heat the kadhai or pan and pour oil. Add chopped onion and fry it till golden brown. Add sliced potatoes, green chilies, ginger and salt. Pour coconut milk into this. Cook in low flame for about 10-15 mins. Now sprinkle black pepper powder and stir well. Cook for 2 mins. When the gravy is getting thick add the thick coconut milk and cardamom powder into this and stir well.
Garnish your dish with curry leave. Serves hot with Veg Pulav or Steamed Rice, Puri, or bread.