Root vegetable gratin has become one of my favorite dishes to bring as a holiday side dish. The more different kinds of multi-colored root vegetables you can find, the more fun it is.
I got the original idea from my brother Mike, who shared with me this recipe from Williams-Sonoma. I mostly follow the recipe, except I only use 2 cups of cream instead of 3, which makes it easier since cream usually comes in 1 pint containers. I buy a variety of root vegetables and just eyeball how many I need based on the size of the baking dish I happen to be using.
This time around, I was able to get the following root vegetables from the Rittenhouse and Fitler Square farmers’ markets:
- Japanese purple sweet potato from Z Food Farm
- yellow sweet potato from Beechwood Orchards
- orange sweet potato from Highland Orchards
- purple potatoes from Z Food Farm
- fingerling potatoes from Z Food Farm
- red potatoes from Z Food Farm
- celery root from Z Food Farm
- carrot from Rineer Farm
- parsnip from Rineer Farm
In the past I’ve also used rutabaga when I could find it. The real treat this year was the purple sweet potato, which was not only brilliant in color but also very sweet. I sliced the vegetables as thinly and uniformly as I could manage without a mandolin. Most of these cook pretty evenly, but the one you need to look out for is the celery root, which tends to take longer to cook than the others. This year I used a vegetable peeler to shave the celery root more thinly than the rest of the vegetables, and that seemed to work well.
I melted 1 tablespoon of butter in a saucepan, then added the 2 cups of cream, 3 cloves of minced garlic, salt and pepper, and nutmeg. I heated this until it started to bubble, then set it aside.
Meanwhile, Tom buttered a baking pan and I started arranging the root vegetables. There are so many ways you can do this, it’s fun to play with the colors and see what you get. One option is to arrange them so all the same colors are together, like my brother did a few years ago:
This year, I arranged mine in concentric rings, with each layer in a different color scheme, so that when the end product was sliced, you’d be sure to get a variety of colors in each bite.
Halfway through, after the second layer, I drizzled half of the cream mixture over the vegetables and sprinkled 1/2 cup of grated gruyere cheese, as well as some fresh thyme and parsley. Then I added the third layer on top of that, and would have added a fourth layer if my pan had been deeper, but decided to stop after three layers (I was only feeding four people, after all).
After the final layer, I poured the rest of the cream mixture, the other 1/2 cup of grated gruyere, and more thyme and parsley.
Now it gets covered with foil and bakes at 400˚F for one hour. After one hour, I removed the foil and let it bake another 30 minutes uncovered. I let it stand another 15 minutes or so before serving.
Delicious and colorful!