Creative glazes and a novel cooking method transform humble root vegetables into exciting side dishes. Be sure to rinse the leeks well to remove all the dirt. Serves 6
1. Adjust oven rack to middle position and heat oven to 450 degrees F. Toss celery root, leeks, jelly, 1/2 teaspoon salt, 1/8 teaspoon pepper, and melted butter in 13-inch by 9-inch glass or ceramic baking dish. Pour water over vegetables, cover with foil, and roast until celery root softens, about 20 minutes.
2. Remove foil, toss in grapes, and continue to roast, tossing occasionally, until vegetables are tender and liquid reduces to a thick glaze, 20 to 25 minutes. Add tarragon and cubed butter and toss. Adjust seasonings and serve.