I have become a big fan of the celery root, also known as Celeriac. Most people I talk to don't know how to even approach the strange looking root.
Here's a recipe that we enjoy frequently, a twist on the traditional mashed potatoes
MASHED CELERY ROOT
1 celery root
dash of cream
Peel the potatoes and chop into pieces. Peel the celery root and chop into similarly sized pieces. Put in a pot, cover with water and boil until the potatoes and celery root are fork tender.
Remove from and drain. Return the vegetables to the pot and add a dash of cream, a little butter (a tablespoon or two) and mash to desired consistency. Taste, add more cream and butter if needed and season with salt and pepper.