Pound (or use a chopper) the ginger and garlic to get a small amount of paste. Add a little water as necessary. You shouldn't need water if using a pestle and mortar. Or use a shop bought paste.
Measure out all your spices, whole and ground and set them aside. Don't forget to lightly pound your black cardamoms, to help them release their aroma.
Measure out the ratan jot and spices and set aside.
Place the the ratan jot on your muslin and tie into a little bundle. If you don't have any muslin, don't worry, see alternative method below.
Slice the ginger into matchstick slices.
Let's Get Cooking!
Heat 2 Tbsp of ghee in a large saucepan on medium heat.
Brown the lamb shanks all over. This will take about 5 minutes, and your kitchen is going to smoke. Open the windows, turn on your extractor, and mind that smoke alarm!
Take the lamb shanks out and place on a plate and set aside until needed.
In the same pot, fry the cardamoms and cinnamon stick for 30 seconds on medium heat. Add 1 Tbsp of ghee if the saucepan is dry.
Tip in the onions and fry for 2 minutes on medium-low heat.
Add the ginger-garlic paste and fry for 30 seconds.
Add the lamb shanks back into the saucepan, along with any juices on the plate (bloody or not). Add the Kashmiri chilli powder, ground ginger and ground coriander, then stir a little to coat the meat. Still on medium-low heat.
On the same heat, add the water, and before it starts to boil, slowly drip in the yoghurt, stirring constantly. I've found that the best way to prevent the yoghurt from curdling is to drop a dollop (about 1 Tbsp) of yoghurt, stir, another dollop, stir, until it's all in. If it curdles, it doesn't matter, your curry will still be delicious.
Bring to a simmer on, increase the heat to medium if you are too impatient to wait for it to heat up. Then, cover with a lid, reduce the heat right down, and cook on this very low heat for 1½ - 2 hours until your meat is fully cooked.
Heat 2 Tbsp of ghee in the smallest frying pan you have on medium-low heat. Place the muslin pouch (with the ratan jot) in the pan and swirl it around to allow the ratan jot to heat up and for the oil to get red. If the muslin is soaking up too much of the ghee, add a Tbsp more.If you don't have any muslin, just fry the ratan jot in the ghee, drain, then add the ginger and fennel, before adding to the recipe right at the end.
When your ghee is a beautiful deep red (a minute or 2, max should do), add the ginger slices and the fennel seeds. Fry for 30 seconds, then turn the heat off.
Discard the muslin pouch, squeezing out the red oil using 2 spoons. Then, pour this beautifully coloured and flavoured oil all over your rogan josh.
Stir the rogan josh, then turn the heat off. Leave to rest for 5 minutes, then serve.
You can finish it off with some coriander leaves, if you like.
The curry will freeze very well, for up to 3 months. It will also keep in the fridge for 2 days.