This recipe has been updated and may differ from what was originally published or broadcast.
Preheat the oven to 375ºF.
Slice the potatoes into 1/4-inch-thick rounds. Peel the celery root and cut into 1/4-inch-thick slices to resemble the potatoes.
Butter a heavy oval casserole dish. Layer the potatoes in the bottom of the dish, followed by the butter and then a layer of celery root. Sprinkle with sea salt. Top with a layer of half of the cheese. Repeat with the remaining potato and celery root. Top with the cream and then the remaining cheese.
Bake until deep golden brown, about 1 hour.