preheat the oven to 190C/375F/Gas5.
Roll out the pastry and line a 20cm/8in flan ring. Prick the pastry, cover it with greaseproof paper and fill with baking beans. Bake for 10 minutes the remove the beans and paper and leave to cool.
Slice the leeks and boil them in lightly salted water for 10 minutes until really soft. Drain and place in a pan. Add the soaked saffron with the butter and drive off the excess moisture by stirring over a high heat.
Boil the fish stock and Noilly Prat together to reduce it to about 25ml/1fl oz. Add the lemon juice, salt and cayenne pepper then beat into the eggs and cream. Line the pastry case with the leeks and sprinkle with crab meat over the top. Pour over the eggs and cream and bake in the oven for 20 minutes. You can serve this either hot or cold.