In a large bowl, mix 1 kg chicken with 2 tbsp ginger–garlic paste, 1 tsp turmeric powder, 1 tsp red chilli powder, and 1–1.5 tsp salt.
Marinate it and set it aside for 30-40 mins to absorb the flavours.
Dry roast 5–6 green cardamom pods, 1 tbsp cumin seeds, and 1 tbsp coriander seeds until fragrant. Grind them into a coarse powder with mortar-pestle or fine powder spice grinder.
Heat 2 tbsp oil in a deep pan or pot. Add the marinated chicken and fry until lightly golden. Remove and keep aside.
In the same pan, add 2 thinly sliced onions. Fry until golden brown.
Add 1 tbsp ginger–garlic paste and sauté briefly. Sprinkle in a little water, cover, and cook for 3–4 minutes, until oil begins to separate.
Return the fried chicken to the pan and stir well. Cook for 5 minutes.
Add the ground spice mix and 2 sliced tomatoes. Mix and cook for another 10 minutes, until the chicken is cooked through and the masala thickens.
Garnish with slit green chillies and fresh coriander leaves. Serve hot with steamed rice, roti, or naan.