Put Oil in a deep dish
Add the Ginger & Garlic Paste and stir well
Now add the Chicken and fry well until the colour changes
Now add the potatoes and fry well
Fry for about 10-12 minutes until cooked
You may add some water if required about 1/2 cup
Once the Chicken is cooked remove the Chicken and the Potatoes. If the Potatoes are not fully cooked, don't panic as it will cook later in the curry
Now in the same dish, you may add some more oil if required or use the same oil
Now fry the onions until golden brown
Add all the spices and fry well until fragrant
Add the tomatoes and stir well until the tomatoes are soft
Now add around 1/2 cup of water and cover the dish until tomatoes and onions are well blended and form a thick curry
Now add the Chicken and potatoes to the thick curry and stir well
Cook on high flame until the oil floats on the surface and the Chicken should be well coated with the gravy
Now add anywhere between 1-1/2 of water depending on how thick you want the gravy to be
Also add the Green chillies at this stage
Mix well and cover the dish
Let the Chicken and Potatoes cook in the curry on medium flame for about 10 minutes or until the Potatoes are fully cooked
Once the Oil floats the Chicken curry is ready
Serve with Rice or Chapatis