Fairly Foolproof Chicken Curry

Right, today I am posting my easy-peasy chicken curry I make, on a regular basis, for my family… and often times for the tea room. It is quick, doesn’t use a LOAD of ingredients but has a nice, complex flavour, all the same. This is a combo of the chicken curry from Anita Pal's Bengali Cookery Page found here http://easyweb.easynet.co.uk/~palwal/homepage.html and the chicken curry from Hugh Fearnley-Whittingstall found here http://www.bbc.co.uk/food/recipes/database/chickencurry_82424.shtml and me messing around... a bit.
Serves 4

Vegetable oil or Ghee
2 large brown Onions, chopped
6 cloves Garlic, squished through a garlic press
1-4 Serrano chile peppers, sliced thinly (to reduce the heat, remove seeds and ribs from inside the chile. Be CAREFUL not to touch your eyes or any place else ‘delicate’ until AFTER you wash your hands, thoroughly. Or use rubber gloves, better still. You have been warned. How much you use will determine the heat, obviously.)
3 teaspoons Ground Cumin
½ teaspoon Cayenne Pepper
1 teaspoon Turmeric
4 boneless skinless chicken breasts, cubed into bite-size pieces (or 8 boneless, skinless chicken thighs, or an entire chicken, jointed into 8 pieces)
3-4 whole Green Cardamom (or 2 teaspoons ground)
2-3 small pieces Cinnamon (or 1 Tablespoon ground)
50-75g whole, fresh Ginger, chopped fine (If you keep your ginger in the freezer, then it’s a doddle to peel it, then to chop it finely while it's still partially frozen. Frozen ginger lasts months frozen, and a week or so fresh. I now only keep fresh ginger for when I am doing a Chinese Chicken Salad, and honestly.)
780g tin of tomatoes and juice, chopped (I buy whole ones and chop myself since it’s cheaper)
1-2 teaspoons of salt or to taste
2-3 potatoes, scrubbed well, or peeled, and cubed into bite-size pieces

Pour enough oil to just cover the base of a dry medium to large saucepan and heat until the oil is very hot but not smoking. Add the onions to the oil. Sauté until the onions begin to caramelise. Add the garlic and chiles and stir until the garlic is turning opaque but do NOT brown. Try not to inhales the fumes as it will be cough-invoking from the chiles! Remove the saucepan from the heat and leave to stand.
Place all the spices (turmeric, cumin powder and Cayenne powder) into a small cereal bowel. Add about half a cup of water and mix. Pour the spice mixture over the onions. Fry on a medium heat until most of the water evaporates but make sure that the spice mixture does not burn.
Add the chicken and stir until all the chicken is coated. Reduce to low heat.
Add the ginger, tomatoes and salt and cook for 10 - 15 minutes. Then add enough water to just cover the chicken. Add potatoes. Place a lid on the saucepan and bring to boil. Reduce to medium heat and simmer for 10 minutes (30 minutes for bone-in chicken pieces) or until the potatoes and chicken are both tender.
Meanwhile, grind the whole cardamoms and cinnamon pieces together in a spice grinder (or use powdered spices.) Add the cardamom / cinnamon powder 10 minutes before the chicken is served. Serve with Basmati rice.