Dice the lamb if needed, then peel and dice the potatoes and set them aside.
Then dice the onion and garlic, crush the lemongrass with the back of a knife and chop finely. Peel and grate the ginger, de-seed and finely chop the chillies, de-stem the lime leaves and chop them finely. Chop half the nuts and crush the cardamom pods.
Colour the lamb in a wok and then set it aside in a bowl.
In a large saucepan, dry-fry the dried spices (turmeric, ground coriander and cumin seeds) for 1 minute, then add half of the oil and mix it together. Add the onion, garlic, lemongrass, ginger, chillies, lime leaves and tamarind paste and cook it for a further 3 minutes.
Boil 200ml of water and dissolve the stock cubes. Add the stock to the saucepan, along with half the cashew nuts, palm sugar, coconut milk, the remaining peanut oil, fish sauce and the lamb.
Simmer it gently for 45 minutes, stirring occasionally. Add the potatoes and cook for a further 45 minutes. Finish the dish with the remaining nuts and some fresh chopped coriander.
Serve with boiled rice and naan bread.