For lamb curry, dry toast whole spices in a small frying pan until fragrant, allow to cool slightly and then grind to a powder in a mortar and pestle. Add turmeric and pound to combine. Rub over lamb and set aside.
Place chillies, lemongrass, garlic and onions in a chopper attachment of a stick blender and puree until they form a paste. Heat oil in a large frying pan with high sides and fry until fragrant. Add lamb and cook until golden.
Add coconut milk, reduce heat to low and simmer 2 hours, covered or until tender. Remove lid after first hour to allow sauce to thicken. Stir occasionally to prevent sticking to the pan.
For naan, place flour in a large mixing bowl, make a well in the middle and add water, yoghurt, salt and baking powder and mix until it forms a sticky dough. Turn onto a floured board and knead for 1 minute, using a little extra flour if necessary. Transfer to an oiled bowl and rest 30 minutes.
Melt butter in a small frying pan and add the garlic. Set aside. Roll dough into a cylinder and cut into 12 golf ball sized balls to make 12 small naan, alternatively you can make 6 regular sized naan. Use a rolling pin and roll each ball out to 3mm thickness.
Heat a roasting pan, brush with garlic butter, place a naan in the pan and brush the top of the naan with garlic butter. Cook 1-2 minutes or until golden, flip and cook for 1 minute or until cooked through. Keep warm, wrapped in foil until ready to use. Repeat.