Cut the root end and the dark green part of the leek away (these can be saved for making broth at another time). Using the white and light green parts of the leek only, cut down the leek lengthwise. You'll see that there are layers in the leeks. Rubbing with your fingers, rinse the muddy part that’s between the layers away. Chop the cleaned leeks into small strips.
Melt the butter in a large heavy bottomed saucepan, add the leeks and saute for 3 minutes over medium heat. Add the wine and a pinch of salt and mix well. Cover and cook for 15 minutes or until leeks are tender.
Add the pepper to taste, and garnish with chopped parsley, if desired.