Heat oven to 190C/fan 170C/gas 5. Cut the potatoes and parsnips into matchsticks or grate them coarsely and place in a large bowl. Stir in the onion, creamed horseradish, chives and yogurt and mix until well combined. Season to taste.
Arrange the vegetable mixture in a 20cm shallow metal tin, cover with foil and bake for 1 hr. Remove the foil, dot the top with the butter and bake, uncovered, for a further 15 mins until the
vegetables are tender and the top is crispy and golden. Serve hot.
Recipe from Good Food Vegetarian Christmas magazine, December 2006