Heat oil in a pan and sauté crushed cardamom, cinnamon, mace, and onions with salt until golden brown.
Add green chillies, garlic-ginger paste, and cook until the raw smell disappears.
Mix in turmeric, chilli powder, coriander, cumin, and tomato purée. Cook until the oil separates.
Add chicken pieces, stir well, and cook until the meat is half-done.
Blend cashews and bird’s eye chillies into a smooth paste. Add to the pan and simmer.
Sprinkle dried fenugreek leaves, add chopped coriander, and pour in cream. Stir gently.
Finish with butter and adjust salt and sugar to taste.
Let it rest for 5 minutes before serving with naan or rice.