I've been making this simple spicy version for years. It is a favourite with the hungry workers in my family as it makes proper doorstep sandwiches and doesn't squidge out when they bite into them! It also works as a filling for flat pasties if you fill them and cook them while still hot out of the pan, then serve them warm. It will make 4 good sandwiches or 4 flat pasties, or will serve 2 with a green salad or cold pasta.
Raisins can be used instead of sultanas. Any curry powder will do, as hot or as mild as you like.