Slice leeks (white part) and onion thinly. Melt butter, sweat leeks and onion until tender. Peel & dices potatoes. Add potatoes & white stock to stock pot and season lightly. Bring to boil, simmer 20minutes. Puree and strain into saucepan / clean pot. Re-boil and whisk in fresh cream. Cool in refrigerator for 3 hours if serve cold. Chive to be garnish on top to serve.