Heat ¼ cup sunflower oil in a large pot over medium heat. Add the chicken pieces, season with 1tsp. salt, and fry until browned. Remove the chicken from the pot and set aside.
In the same pot, add the finely chopped onion and sauté on medium heat until translucent. Add ginger and garlic paste and fry until fragrant.
Add the browned chicken back to the pot. Stir in the chopped tomatoes, cumin powder, coriander powder, garam masala, red chilli powder, turmeric powder, half a teaspoon salt, green chilli, and chopped coriander. Mix well to combine all the ingredients. Add ½ cup water.
Cover the pot and simmer on medium heat for 20 minutes, stirring occasionally to prevent sticking. Ensure the chicken is cooked through.
Uncover the pot and increase the heat to medium-high. Continue cooking for another 5-10 minutes until the curry thickens to your desired consistency.
Serve the chicken karahi in a bowl. Garnish with cilantro and thinly julienned ginger root. Enjoy with naan or rice.