Heat oil in a large karahi or wok. After the oil begins to shimmer, lower heat and stir in garlic. Fry for a few seconds till it browns slightly (make sure it doesn't burn).
Add green chilies and ginger paste. Stir to make sure paste doesn't burn. Add cumin seeds and fry for a few seconds.
Turn the heat up high, and add chicken and salt. Stir till it's no longer pink, about 10 minutes.
Add chopped tomatoes and stir continuously for about 10 minutes.
Add red chili flakes, black pepper and garam masala powder. Check for salt.
Once the tomatoes have broken down, let the mixture simmer for another 5 minutes on high heat till it has reduced in volume.
Add cilantro and yogurt. Keep stirring till the tomatoes have become jammy.
Remove from heat. Garnish with cilantro, green chilies, and julienned ginger and serve hot, with naan/chapati, preferably in the karahi itself.