Re-heat the oil in until the oil just starts to shimmer.
Add the onions and stir every few seconds. Fry until the onion edges turn brown.
Stir in the garlic ginger paste. Cook until the garlic ginger paste stops sputtering. This should take around 30 seconds.
Turn your heat down to medium low and add your spice mix. This is why you need to use all the oil. You want to fry your spices. Too little oil and you risk your spices sticking or burning. Nothing you can do will fix burned spices.
Cook your spices for about 30 seconds.
Add the Indian hotel curry gravy. Stir it really well to get the oil to combine with the curry gravy. You want everything mixed together at this point. Bring to a simmer.
Add the chicken. Cover loosely and cook for about 5 minutes.
Add the green chilies, pre-cooked onions and cilantro. Continue to cook until the chicken is cooked through. This should take somewhere between 2 to 5 minutes depending on the size of your chicken pieces. As always it is best to use an instant read thermometer and target an internal temperature of around 175F for thighs.
At this point your dopiaza sauce might be a little thick. Stir in chicken stock or water, a tablespoon at a time to get the consistency you want. As much liquid as you need. This step is feel. You want your dopiaze sauce lush.
Garnish with the fried onions and bit of cilantro if you like.
Serve with rice, dal and Indian flatbreads of your choice.