Preheat the oven to Gas Mark 3/ 160°C. Heat half the oil in a flameproof casserole with a lid over a high heat. Add the beef in batches and fry until nicely browned all over. Transfer to a plate and fry the rest of the meat. Set aside.
Reduce the heat to medium and add the remaining oil to the casserole. Add the onion and fry for 6-7 minutes until softened and just beginning to brown around the edges. Following this, add the ginger and garlic and fry for 1 minute, and then add the spices and fry for another minute. Add the coconut cream, a tablespoon at a time, frying for about 30 seconds between each addition.
Return the beef to the pan and stir in the stock, sugar, tamarind and Thai fish sauce. Season to taste, cover with a lid and place in the oven for 1 hour. Remove from the oven and stir in the potatoes and cook for another 45 minutes to 1 hour or until the beef is meltingly tender but still holding its shape and the potatoes are cooked through and tender.
Spoon the curry on to warmed plates with the rice and scatter over the coriander and chilli rings to serve.