- Preheat the oven to 150°C.
- Whisk the ginger garlic paste, Greek yoghurt, turmeric and salt together and stir through the lamb. Cover and leave for a few hours, preferably overnight.
- In a small saucepan bring the cashews, tinned tomatoes, tomato paste and 200ml of water to the boil. Reduce the heat and simmer for 10 minutes, then blend to a smooth puree and set aside.
- Find a good heavy bottomed casserole or saucepan with a lid and pour in the oil. Toast the spices for a few minutes until aromatic, then add the onions and fry, stirring regularly, for roughly 10 minutes or until lightly browned.
- Stir through the ginger garlic paste and cook for a minute or so until aromatic, then add the ground spices and stir through the onions, cooking everything out for another minute or so.
- Add the lamb and stir continually to brown all over, then add the cashew tomato paste and enough water to cover the lamb.
- Add the bay leaves and stir everything together, then place the lid on top and pop in the oven for 3 or so hours until the lamb has softened and is coming off the bone. Carefully remove the bones and stir through the coconut cream, then season with salt to taste. Set aside to cool.
- While the lamb is cooking, whisk together the flour, salt and turmeric.
- Place the flour mixture on your (cleaned) worktop and use your fingers to make a well in the centre.
- In a small bowl mix sour cream, vinegar and iced water, then pour the mixture into the well you created. Gradually bring the mixture in from the sides. If you've got a bench scraper (or wide bladed knife), use this to chop the mixture together. When coherent enough to knead, briefly bring it together with your hands into a dough. Wrap in clingfilm and set aside for at least an hour in the fridge.
- Preheat the oven 180°C.
- Roll out the pastry to around 1.2 cm thick and cut it into roughly 10cm circles.
- Use some egg wash to brush around the edges and load up the centres with the curry.
- Lay more pastry over the top, cut out the circles and crimp the edges with a fork. Brush with egg wash and sprinkle with nigella seeds.
- Bake for 30 minutes or so until the pastry has risen and they're piping hot inside. Serve with the raita and green chutney.