Pre-heat oven to 200°C / 180°C fan. Grease a square baking dish (roughly 23cm (9 inch)) with butter.
In a small bowl, mix together the cream, garlic, thyme, salt, pepper and 1/2 of the grated Dubliner Vintage.
Arrange the slices of potato, beetroot and parsnip in the baking dish (you can alternate the slices or simply do a row of each veggie).
Pour over the prepared cream mixture then cover the dish with tinfoil and bake for 1 hour.
Remove tinfoil and sprinkle over the remaining cheese then return to the oven and bake until the cheese is melted and golden, about 15-20 minutes.
Allow to cool for about 10 minutes before serving.