So literally this recipe has so many new ingredients I would never have expected and in all honesty I did not even know off. My aunty made this the other day, and said it was a mash up of 2 recipes. Now I will probably never make butter chicken any other way but I will swear the smell of this dish and the taste will blow your mind!
Now after saying this I do know some of the ingredients are not commonly known to most and won't be found just about everywhere. But I will mention places you can check, and remember there is always online shopping when it comes to such things.

For the paratha if you live close to Indian takeout places you can simply order it, for us who live no where close to Indian restaurants we gotta make it, I think the best is to make a naan recipe, and for more of an authentic feel you want to give to the meal shape it weirdly lol.

• Marinate the chicken pieces over night, usually chicken fillet cut into cubes are used. 
• Braise some sliced onions till golden brown, than add your marinated chicken to the pot, you may add some water so it does not burn out while cooking. 
• When half way cooked add tomato puree (how much will depend on the quantity being made - be careful you don't add so much because the taste may over power the spices).
• When almost done add 2 Tb Kasoor methi, 2 Tb brown sugar and 3 Tb crushed cashews and give a boil. 
• Lastly, add your fresh cream, stir and give another boil so all the flavours and spices can blend well together.
• Garnish with fresh coriander, paratha and yoghurt chutney (yoghurt and ground green chillies mixed together).

• When it comes to the Tandoori Masala depending on how much you are looking, do not only add a few teaspoons. Tablespoons will do, and the main taste in the dish is tandoori, so be very generous. 
• Mace is not the same as nutmeg so please don't get it confused. I am not sure if its sold in supermarkets in a spice bottle. I do know its available at spice shops. A pinch is more than enough. 
• Kasoor Methi sold in boxes at supermarkets and spice shops, if you cannot find in your area you can buy online. The box does go a long way because you don't use that much or in every dish. Its green and looks like dry parsley.