Peel and boil the kumara in salted water until tender. Drain. Mash or put through a food processor. Add milk. Saute onion in butter until soft and transparent. Add to the chowder. Add the can of creamed corn and bring slowly to the boil. Stir frequently or the soup will catch. Add more milk if necessary but the soup should be thick. Stir in cream and gently reheat. Serve in warm bowls and garnish with a little parsley.
Serves 6.