1. Heat the oil or ghee in a karahi, wok or wide heavy pan over a medium-high heat. Add the onion and cook for 8–10 minutes until golden at the edges.
2. Add the garlic, ginger and green chillies. Fry for 1–2 minutes, stirring constantly, until fragrant.
3. Add the chicken and salt. Cook hard for 6–8 minutes, stirring often, until the chicken is sealed and beginning to catch lightly on the pan.
4. Stir in the cumin, coriander, chilli powder, turmeric and black pepper. Fry for 1 minute so the spices bloom in the oil.
5. Add the tomatoes and cook uncovered for 15–20 minutes, stirring often, until they collapse into a thick masala and the oil begins to separate at the edges.
6. Lower the heat to medium. Add a splash of water if the pan looks dry, then simmer for 8–10 minutes until the chicken is cooked through and tender.
7. Stir in the spinach in handfuls, letting each addition wilt before adding the next. Cook for 2–3 minutes only, so the spinach keeps some colour.
8. Stir in the yoghurt, if using, then add the butter, garam masala and crushed fenugreek leaves. Simmer gently for 2 minutes until glossy.
9. Finish with fresh coriander, ginger matchsticks and a squeeze of lemon. Serve hot with naan, roti or pilau rice.

Multi-Cooker Option

Ninja Foodi / Air Fryer

Use the Sear/Sauté function rather than pressure cooking, as karahi gets its character from open-pan reduction.

1. Set the Ninja Foodi to Sear/Sauté on high. Heat the oil or ghee, then cook the onion until golden.
2. Add the garlic, ginger, chillies and chicken, then fry until the chicken is sealed.
3. Add the spices and tomatoes. Cook uncovered on Sear/Sauté for 18–22 minutes, stirring often, until thick and glossy.
4. Add the spinach, butter, garam masala and fenugreek. Cook for 2–3 minutes more.
5. The chicken should reach 74°C internally before serving.