salt and pepper
1/2 pint milk
Chop the potatoes into smallish cubes and then chop the leeks. Sweat them in a large pan in a knob of butter. When slightly browned add the veg stock, season and simmer.
When the vegetables have softened blend the soup using a hand blender. I like to leave it pretty rough so there's still some chunks of potato to enjoy.
Lastly add the milk, this thickens it a little and makes it a touch paler. I use skimmed milk, but for a richer version use full fat.