It's well past celeriac season, but I had one lingering in the fridge and with the weather having taken a rather cold turn, mashed potatoes seems appealing (I served them with slow cooker braised beef shanks, yum!) The combined flavor of the potatoes and celeriac was pleasant, and as a bonus, my kids chowed down even though they normally reject celeriac.
Feel free to swap in other root vegetables for the celeriac if you like: parsnips, turnips, rutabaga, etc. Each will bring its own unique flavor to the mix.
1 large celeriac root, peeled and cubed
1 1/2 lbs potatoes, cubed (peel if you like; I don't)
Up to 1/2 cup milk
2-3 Tbsp butter
Salt and pepper to taste
Parsley to taste (fresh or dried; optional)
Cook the celeriac and potatoes in a large pot of salted boiling water for about 15 minutes or until tender. Drain and return to the pot.
Mash the celeriac and potatoes with a potato masher, adding milk and butter until desired consistency is reached. Add salt and pepper to taste, plus parsley if desired.