Add the onion, garlic, and ginger to a mini food processor and blend to a paste.
Heat the ghee (or oil) in a large frying pan over a high heat. Add the onion mixture and fry for 3-4 minutes, stirring occasionally, until starting to brown at the edges.
Add the chicken and cook for 2-3 minutes, stirring often, until sealed.
Turn the heat down to medium and add the cinnamon, curry powder, chilli powder, paprika, ground fenugreek, and tamarind paste. Cook for 1 minute, stirring constantly.
Add in the lemon juice, sugar, salt, passata, tomato puree, chopped chillies, and chicken stock. Bring to the boil, then simmer for 10 minutes.
Serve with fresh coriander, a slice of lemon, and boiled rice.