Combine half the ginger, half the garlic, half the turmeric, half the lemon juice and half the oil in a large bowl with ALL the cumin, garam masala, ground coriander, paprika, chilli flakes and yoghurt.
Add the chicken, turn to coat in marinade.Cover and refrigerate for at least 30 minutes.Preheat oven to very hot (220C/425F).Cook chicken in lightly oiled shallow flameproof baking dish, uncovered, 10 minutes.(With the marinade).
Heat remaining oil in large saucepan, cook onion, chilli powder, fenugreek, remaining ginger, garlic and turmeric, stirring, until onion softens.
Add tomatoes (with their juice), cinnamon, green chillies and remaining lemon juice.Simmer, covered, for 10 minutes.Stir in cream and honey, simmer, uncovered, for one minute.
Add chicken to curry, simmer about 5 minutes or until chicken is cooked through.
Remove from heat, stir in fresh coriander, serve over basmati rice, garnish with fresh coriander.