“This dish is inspired by something we have on our menu during the fall and throughout the holiday season. It’s a nice way to showcase seasonal, cold weather vegetables like celery root and rutabaga, two of my favorites. We use a really great local Gruyère-style cheese from Kenny’s Farmhouse called Norwood, which melts nicely.”
- Make Mornay Sauce by sweating shallots in butter with 2 pinches salt in heavy-bottomed saucepot. Add flour and cook, stirring occasionally, about 5 minutes. Whisk in milk, cream, and spices. Add thyme sprig. Bring to simmer, stirring constantly. Remove from heat, discard thyme, and whisk in cheese, reserving 2 tablespoons cheese to top gratin. Purée in blender until smooth. Keep warm.
- To assemble, preheat oven to 400 degrees.
- Peel root vegetables, keeping potatoes submerged in water to prevent browning. Butter casserole dish and ladle in a thin layer of Mornay. Slicing as you go (use a mandoline or very sharp knife), slice Russet potatoes into enough ⅛-inch slices to cover bottom of a casserole dish. Sprinkle with salt.
- Cover potatoes with thin layer of Mornay. Repeat with remaining vegetables, covering each layer with a thin layer of sauce, until vegetables are about 1-inch from top of dish. Sprinkle with reserved Gruyère and bread crumbs.
- Cover with foil and bake for 1 hour, until vegetables are just tender when skewered with toothpick. Remove foil and return to oven for about 20 minutes, until golden brown. Let cool for at least 10 minutes before serving. Sprinkle with celery leaves and orange zest.