Chestnuts are one of winters treats, but peeling them is a chore. Luckily, you can buy jars of vacuum-packed peeled chestnuts, which are of excellent quality and all ready to use. If you do so, skip Step 2.
2 pounds Brussels sprouts
1 pound chestnuts
4 tablespoons unsalted butter
1 cup heavy cream
1/2 teaspoon salt
1/4 teaspoon freshly ground pepper
Trim the Brussels sprouts. Cut a tiny X in the stem end of each with the tip of a small knife. Bring a large saucepan of salted water to a boil. Add the sprouts and cook for 7 minutes, until they are about three-quarters cooked. Drain, rinse under cold water to cool, and drain well. Chop very coarsely.
Heat the oven to 375°F. Cut an X into the flat side of each chestnut. Put in a shallow baking pan and roast for 15 to 20 minutes, until the ends of the cut shells curl back. As soon as they are cool enough to handle, peel and chop the chestnuts very coarsely.
In a large saucepan, melt the butter in the cream. Add the Brussels sprouts and chestnuts; season with the salt and pepper. Cook over moderate heat, stirring occasionally, until most of the liquid is absorbed, 5 to 10 minutes. Season with additional salt and pepper to taste, cover, and set aside for up to 3 hours or refrigerate overnight. Reheat in a saucepan over moderate heat or in a gratin dish in the oven with your roast before serving.