Preheat the oven to gas 6, 200°C, fan 180ºC. Put the carrots in a single layer in a baking dish. Pour over the oil, maple syrup (or honey) and 75ml (3fl oz) water. Dot the butter over the top. Season, cover with foil and bake for 20 minutes.
Remove the foil and shake the pan. Roast for 20 minutes more without foil until most of the liquid has evaporated. Sprinkle with parsley and serve.