Peel and cut the kumara into 2 cm thick cubes. Place in a saucepan, cover with water, and add the salt. Bring to the boil and cook until just tender. Refresh under cold water, and strain in a colander. Then pat dry with a kitchen paper towel.

Heat a large frypan over a medium heat, add the butter and ham pieces and fry until they take on a little colour. Remove from pan and set aside. Add the onion to the pan and fry until softened, then add the kumara. Fry for another minute then add the ham and peas. Pour over the cream, followed by the parmesan and thyme. Simmer stirring gently, until the cream reduces. Season with salt and pepper, and serve immediately garnished with thyme sprigs.