Set your slow cooker to the sauté function. Add the ghee and, once hot, fry the onion until translucent. You want to get it as soft as possible. This is where a lot of the flavour for the curry comes from. Give 10 minutes cooking time, stirring regularly.
Add the meat, ginger, garlic, chilli, turmeric, coriander and garam masala to the bowl. Season with salt and pepper.
Stir constantly, moving the meat and spices in and around the onion mixture, for up to 5 minutes. Depending on the size of your slow cooker, you may need to do this in batches.
Add the yoghurt and then the stock, close the lid and cook on low for up to 10 hours.
Garnish with the chilli, coriander, fried garlic and curry leaves, and serve with rice, poppadoms, chutney, fresh lime and your favourite choice of sides.