In a saucepan combine the first five ingredients. Bring to a boil and simmer for 10 minutes. Strain and reserve the liquid
Place the leeks in the pan and add the strained lemon stock. Bring to a boil, then cover and simmer for 10-15 minutes or until the leeks are tender, but not mushy. Drain and transfer to a serving dish.
Combine all the ingredients in the top of the double boiler and cook, stirring, over barely simmering water until the sauce thickens, about 10-15 minutes. Pour the sauce over the leeks and serve hot.
Serve as a side or with a crusty warm bread.