Take a pan put 2tbsp oil and heat it.turn the flame medium then add crushed garlic,ginger and green chillies.saute for 1 minute then add red chilli powder, turmeric powder and chat masala.saute for 1minute then add mashed potatoes mix well and cook on medium flame for 3-4 minutes. Add chopped coriander and mix well.turn off the flame and keep aside.