Cut 500 grms of potatoes into thin round slices.  Wash them ,dry on a cloth and season with salt and freshly ground pepper.  Put in a buttered pan in layers with the shredded white part of two big leeks and two tablespoons of chopped parsley.  Add bouquet garni and chicken stock or water.  Scatter 500 grms of butter in tiny dabs.  Bring to the boil on the stove, cover with a lid and cook in the oven.  This is a great potatoe dish with a difference to accompany fish.