Mix the chicken, kafir, lime juice, and chilli powder in a large, non-metallic bowl or plastic bag. Set aside to marinade while prepping the rest of the spices.
In a flat pan, medium heat, gently roast (stirring frequently) the roasting spices until they darken slightly.
Let cool and put in a coffee grinder and grind into a coarse powder.
Add the coriander, cumin, amchoor powder, and tumeric and mix.
Heat a few tbsp of vegetable oil in a deep pan on medium heat.
When hot, add the onions and half of the spice mix. Saute until the onions turn light brown.
Add garlic and ginger and fry for about a minute.
Add the can of tomatoes and saute until most of the liquid is gone.
Add the chicken to onion mix, along with the other half of the spices, and let cook until the flesh begins to turn white.
Add 1 cup of the chicken stock and the fenugreek leaves. Saute until it begins to thicken, stirring occasionally.
When the mix begins to thicken, add in another 1/2 c of the stock.
Let begin to thicken again, add the tomato paste / ketchup and the other 1/2 c of stock.
Let cook until sauce has reduced and makes a nice thick gravy and the chicken has cooked through.
Finish off with a squirt of lime juice and the melted butter, stirring to mix.