This is is a good side dish for any special occasion like Thanksgiving or Christmas but the leftovers can be perfect as a small drinking dish. This is a rather unique mashed potato dish since it includes a root bulb of a special type of celery plant called “celeriac” and has a nice crust of Parmesan cheese on the top.
We served this as a “drinking snack” along with my wife’s holiday stuffing and bacon (which was placed over the stuffing when it was baked in a casserole. The bacon was further crisped in a frying pan before serving–decadent).
I learned this recipe from a friend who served this when we were visiting them a long time ago. I do not know where the original recipe came from. Making this dish is relativly easy except that you need celeriac (below left) which appears to be available in Japan, although I have never seen it there while I lived in Japan. After peeling off all the rootlets and skin, you get the object shown on the right.
I use white potatoes (6 medium) but Yukon gold is another kind you may like to use. I peel and cut the potatoes in quarters, parboil and rinse them in running cold water. This removes the excess starch and prevents the mashed potato from becoming too gooey or gummy (skip this step if you like your mashed potatoes gooey and gummy). I dice the celeriac (1/2 inch dice) and cook it with the potatoes in salted water for 20-30 minutes or until both are soft and mashable. I drain and mash them together. I season the mixture with salt. I could use cream or butter or both but I add creme fraiche (2-3 tbs) and mix. I put the mashed potato mixture in a shallow buttered baking dish (I used Pyrex as seen below) and smooth the top using a rubber (silicon) spatula. I grate Parmesiano Reggiano on it. You grate enough cheese to cover the surface of the potato so that it will make a nice crust. Broil it for 5-10 minutes until the cheese melt and developed brown crust (below). Let it stand for 5 minutes so that the parmesan cheese will harden to make a nice crust.