A Goan/South Indian dish with a Portuguese history combined, I started with a Pat Chapman recipe and modified it to my taste. I was trying to come as close as possible to the vindaloo dishes I enjoyed at a particular Indian restaurant in Britain, and this is the result.
There are some spices that I've rarely encountered at food stores locally and had to order through the internet, namely asafoetida and cassia bark, but these can be subbed with garlic powder and cinnamon, respectively with minimal effect.
I've also found that the type and quantity of hot peppers used contribute significantly to the taste of the dish. Times I've tried to make it in a mild form so others could eat it without having to call the fire department, it didn't turn out very well. For this reason, I consider the type and quantity of pepper to be irreplaceable and that you have to like it HOT to really enjoy the dish.
I use chicken for the meat, but I've seen (not tried) it offered with pork, lamb, and shrimp.
Fresh ground spices always work best as well as fresh garlic and cilantro.