- Heat the oven to 400°F. Spread the butter in a 3-quart shallow baking dish. Place the squash, potatoes, celery root and leeks in the prepared dish.
- Heat the broth, cream, thyme and nutmeg in a 2-quart saucepan over medium heat to a boil and season to taste.
- Pour the broth mixture over the vegetables and toss to coat.
- Bake for 25 minutes. Reduce the temperature to 350°F. and bake for 40 minutes or until the top is golden brown and the vegetables are tender. (If the vegetables are browning too fast in the first 25 minutes, cover the dish loosely with foil.)
- Sprinkle with the cheese. Let stand for 10 minutes.
Time-Saving: Use a Japanese mandoline to slice the vegetables to an 1/8-inch thickness.