Fill a large saucepan with water, add salt and bring to the boil. Add the carrots, leek, peas and potatoes, then add vegetable stock cubes and stir to dissolve.
Cover, reduce heat to medium and simmer for about 40 minutes (until vegetables are tender).
When vegetables are cooked, remove about 225ml of liquid from pan and set aside. Puree remaining soup with a hand blender or in a food processor until consistency is velvety smooth; season with salt and pepper to taste. If soup is too thick, add the reserved stock till desired consistency is reached and blend again.
Chill the soup in the fridge thoroughly, for 3 hours or overnight.
Pour the soup into small glasses, garnish with raw vegetable curls or chopped herbs if you like and serve with a straw!