Fettucine with Leeks and Cream

Why I Love This Recipe
Poor man's asparagus. A totally under-used vegetable, with a delicate flavour and a wonderful texture as long as it's not overcooked. A bit of trouble cleaning but not really difficult. Leeks, national plant of Wales.
Ingredients You'll Need
500-750 g leeks
3 tablespoons best butter
250 ml (1 cup) creme fraiche
Grated peel and juice of 1/2 lemon
salt and pepper to taste
grated Parmesan or shavings
as much pasta as you like to cook (I would say the sauce is enough for about 4 good helpings)
Directions
Clean the leeks by taking off at least one outer layer of leaf and skin. Cut off the tough green leaves, leaving a tuft at the top. Cut a slit into the tuft vertically, barely cutting into the white. If you look at the leek from the top it will have a sort of boat shape - cut along the length of the boat shape, and open out the leaves. You will see mud and sand stains inside. Wash these meticulously, take off the roots at the other end and voila!
Cut the leeks crosswise into 1/2 inch slices. Saute them briefly in 2 tablespoons butter till they are just wilted.
Stir in the creme fraiche and let the sauce bubble for 3-4 minutes.
Set aside.
Cook your pasta and put into a hot bowl with 1 tablespoon butter and a spoonful of the pasta water.
Reheat the sauce, stir in the lemon peel and juice, salt and pepper to taste and serve with grated Parmesan or shavings.