This is rather like a gratin dauphinoise, made with parsnips rather than potatoes. You could also try making it with turnips, or a mixture of parsnips and turnips if you like.
Preheat the oven to 190°C/gas 5. Peel the parsnips and cut them into rough 2-3 cm chunks, cutting out the hard core. Pour the cream and milk into a pan and add the garlic, nutmeg, and some salt and pepper. Slowly bring to the boil, then remove from the heat and leave to cool a little.<