Heavy cream is the most traditional liquid in gratins, but milk or stock, or a combination, can replace half the cream for a lighter result. In this recipe, the liquid is infused with thyme to help its flavor disseminate more effectively since the vegetables will soak up the liquid; this step can be omitted but it does make a difference.

　　

Ingredients

Serves 6

　　1 to 2 tablespoons unsalted butter (optional), plus more for baking dish

　　1 1/2 cups heavy cream, plus more if needed

　　3 sprigs robust herbs such as thyme or sage

　　2 pounds total potatoes (preferably russets) and turnips, peeled and thinly sliced

　　Coarse salt and freshly ground pepper

　　

Step 1

Infuse liquid Heat oven to 375°F and butter a 2 1/2-quart oval gratin dish or 9 by 13-inch baking dish. Bring cream and thyme to just under a boil in a small saucepan, then remove from heat and let stand 30 minutes. Strain through a fine sieve and discard solids.

　　

Step 2

Assemble Arrange the vegetable slices in an overlapping fashion in the baking dish, alternating them and seasoning with salt and pepper as you go. Dot with butter, if using. Pour cream over top (it should almost cover the vegetables; add up to 1/2 cup more if necessary) and cover tightly with parchment-lined foil.

　　

Step 3

Bake Bake until vegetables are tender, about 45 minutes, then remove foil and bake until golden brown and bubbling, about 15 minutes more. Serve at once.

　　Reprinted with permission from Martha Stewart's Cooking School: Lessons and Recipes for the Home Cook by Martha Stewart. Copyright © 2008 by Martha Stewart. Published by Crown Publishing. All Rights Reserved.Martha Stewart is the author of dozens of bestselling books on cooking, entertaining, gardening, weddings, and decorating. She is the host of The Martha Stewart Show, the Emmy-winning, daily national syndicated program, and founder of Martha Stewart Living Omnimedia, which publishes several magazines, including Martha Stewart Living; produces Martha Stewart Living Radio, channel 112 on SIRIUS Satellite Radio; and provides a wealth of ideas and information on www.marthastewart.com.