In a mixing bowl, add the chicken pieces and the ingredients of the first marinade [ginger garlic paste, salt, and lemon juice], and mix them well together. Allow the chicken to marinate for 30 minutes.
After thirty minutes, proceed with the second marinade: add the yogurt, lemon juice, salt, Kashmiri chili powder, and oil. Mix well and allow the chicken to marinate for at least one hour, ideally overnight if you are preparing in advance.
Once ready, grease a grilling pan and grill the chicken on both sides until cooked. Try to achieve dark cooking lines, which will give a barbecue/tandoor effect.
Prepare The Butter Chicken Sauce
In a large saucepan, add all the ingredients for the curry base [water, tomato, onion, bay leaf, cinnamon stick, black cardamom, cloves, green cardamom, garlic cloves, ginger, Kashmiri chili powder, butter and cashew nuts]., mix well and bring to a light simmer.
Allow the ingredients to simmer in the saucepan with a lid on for 20 minutes [or until the tomatoes are mushy - whichever is longer].
Allow the curry base to lightly cool down, then add to a blender and blend till smooth.
Pass the blended curry through a fine grain sieve, straining all the pieces that have not blended. This step is extremely important to achieve a silky smooth butter chicken sauce. Set the curry sauce aside.
Final Steps
In a large pan [the same one can be used], add the butter and allow it to melt on a low flame; once the butter has melted, add the remaining chopped fresh ginger and the 3 slit green chilies. Sautee these together until the rawness of the spices has gone.
Next, add the smooth curry sauce to the pan together with a little water (½-3/4 cup - 100-200ml) and the half teaspoon of sugar [this helps with the acidity of the tomatoes]. Leave the saucepan on low flame with a lid to simmer for 10 minutes.
Put the dry fenugreek leaves on a paper towel and warm up in the microwave for about 20 seconds, then remove and crush between the palms of your hands and into the curry. [Putting the leaves in the microwave will allow the leave to release their smell as well as making them easier to crush]
Mix well the curry sauce and add the chicken; mix the chicken in the curry sauce allowing it to be fully coated and simmer on low flame for 4-5 minutes, until thoroughly warm.
Lastly, garnish the curry with cream and freshly chopped coriander.
Serve with fragrant steamed rice, or flatbreads, such as chapattis, parathas, naan, or roti.
Notes
Storage: Butter chicken can be stored in the fridge in an airtight container for up to 3 days, or in the freezer for up to three months.
Chicken: Chicken breast can be used instead of thighs, although, as it contains less fat, it is important to allow it to marinate for at least 3 hours. This way the yogurt will penetrate well and help keep the meat moist.
Cream: Use heavy whipping cream, thickened cream, half and half, or double cream, ensuring they are unsweetened. Coconut cream can be used, but the taste will slightly change.
Kashmiri Chili Powder: As this is a relatively mild dish, Kashmiri chili is used, which is not as spicy as red chili powder, but has a very bold color. For a spicier result, use Indian red chili powder.
Vegetable Oil: Any unflavored oil, such as sunflower oil, can be used.
Whole Spices: Should you not have bay leaves, cardamom [black and green], cloves, and cinnamon, you can use 1 teaspoon of garam masala instead.
Cashew Nuts: These give richness to the curry, however, they can be skipped [the curry will be less dense]. They can also be substituted with almonds [peeled], pinenuts, or hazelnuts.
Cooking The Chicken: Should you prefer, the chicken can be also cooked on a skillet, in the oven, or on the barbecue. The lucky ones can use a tandoor for a 100% authentic experience.
Sieve: Passing the curry sauce through a fine-grain sieve is perhaps the most important part of the recipe, as it allows to achieve a silky consistency. Try not to skip this step.
Cream And Butter: The quantities used can be increased or reduced, as preferred. These amounts in the recipe offer a very tasty recipe, without making the dish too greasy.