Cut chicken into one inch pieces and add the lemon juice, green chilli paste and salt, mix well and keep aside.
Blend the coriander leaves, mint leaves and spinach into a paste and add this to the chicken pieces. Marinate this for at least 1 hour.
Grill or bake this chicken pieces lightly at 180 C for about 20 minutes. (reserve any leftover paste to use it later in the curry). Or optionally, omit this step and proceed with the rest of the recipe.
Heat butter in a pan, fry onions till translucent. Add the garlic and ginger and sauté for 2 minutes.
Add garam masala, salt and the chicken pieces and mix well. (Add any reserved leftover paste from the marinate now).
Add the fresh cream and stir gently.
Remove from the flame. Serve hot with Nan or Rice.