Method

1. Preheat oven to 180°C. Brush a 35 x 20cm baking dish with ½ the butter. Using a sharp knife or mandoline, finely slice celeriac, swede, potato, onion and garlic. Put vegetables in a large bowl with thyme, parmesan and remaining butter. Season with salt and pepper and stir to combine.

2. Transfer vegetable mixture to prepared dish, then pour over stock. Bake for 45 minutes or until all liquid has been absorbed and vegetables are tender. Stand for 20 minutes before serving.