Combine all the ingredients under Chicken marinade in a large bowl. Mix well so that the chicken is evenly coated. (You can cook the chicken right away, or set it aside to marinate for 30 minutes.)
In a hot pan with olive oil, add in the marinated chicken and cook for about 5 minutes, or until completely cooked. Keep stirring the chicken to ensure that it is lightly and evenly charred. Set the cooked chicken aside in a large bowl.
In the same pan, add olive oil and cumin seeds and let it crackle. Then add in the finely chopped onion and sauté until they are lightly browned.
Next, add in the finely chopped green chilis and sauté for a minute. Add the ginger-garlic paste and keep stirring.
Once the raw smell of the ginger-garlic paste fades, add in the tomato purée. Season it with salt and mix well. Cover the pan and cook on low heat for about 5 minutes.
Add the garam masala, ground coriander, ground cumin and turmeric and mix well.
On medium heat, add water and cook the curry for 3-5 minutes without a lid. Stir occasionally. Now add in the heavy cream and ¼ cup of cilantro.
Add the cooked chicken to the tikka masala curry. Let it simmer on low heat for 2-3 minutes.
Garnish with chopped cilantro. Serve with white rice or naan.