I used the BBC Good Food recipe as a starting point, but haven't looked at it in years so it might be a lot different in practice. Here it is:
About 500g beef mince
400g tin of tomatoes
400g tin of kidney beans
About 2 heaped tablespoons of tomato puree
A couple of squares of 85% dark chocolate (although 70% is fine)
2 small red onions, diced, and 2 red peppers, diced (I prefer to use sweet red peppers but they are slightly more expensive)
About 300ml of beef stock
1 tablespoon each of cumin, sweet smoked paprika, chipotle chilli powder and garlic granules (or 3-4 fresh cloves, grated). About a teaspoon of marjoram, or oregano if I don't have it.
Basically, fry the mince, season and set aside. Fry the onions and peppers, then when the onions are translucent add the spices, fry for another new minutes then add the puree, give it a stir and return the beef to the pan. Add the tomatoes and kidney beans and the beef stock (if you're having problems with it being watery, add half the stock and keep topping up if it dries out while cooking, but I find 300ml is usually about right).
After it comes up to a boil, add the marjoram and chocolate. Let the chocolate melt on the surface then stir it in, then simmer for a minimum of 30 mins. Sometimes I adjust the spices after 30 minutes and add more to taste depending on who is eating it (i.e. if I'm making it for the kids I use a tablespoon of mild chilli powder and a teaspoon of chipotle, if it was for me and my husband I'd use 1.5/2 tablespoons of chipotle). The most common thing I add more of is cumin and paprika though.
It's one of the dishes everyone seems enjoy / request the recipe for so I must be doing something right!