Parsley root is often cooked similarly to celery root (celeriac). Try it roasted, boiled, braised, pureed/mashed or in soups & stews. It can be prepared peeled or unpeeled (but scrubbed).
Pair parsley root with ingredients like other root vegetables (potatoes, sweet potatoes, carrots, beets, parsnip, celery root, etc), fennel, truffles, garlic, cabbage, barley, braising cuts of meat (especially pork), poultry, cinnamon and/or thyme.