Ingredients

serves 6

　　6 medium sweet potatoes (8 ounces each)

　　1 tablespoon unsalted butter

　　4 large yellow onions, cut in half, then into 1/2-inch-thick half-moons

　　3 tablespoons sugar

　　1 teaspoon coarse salt

　　1/4 teaspoon freshly ground pepper

　　2 tablespoons balsamic vinegar

　　1 1/2 ounces freshly shaved Parmesan cheese (about 1/2 cup)

　　

Step 1

Preheat the oven to 450°F. Place the potatoes on a baking sheet; bake until tender, about 45 minutes. Meanwhile, melt the butter in a large nonstick skillet over medium-low heat. Add the onions; cook until soft, about 15 minutes. Sprinkle with the sugar, salt, and pepper; toss to coat. Continue to cook, stirring occasionally, until the onions are very soft and caramelized, about 1 hour more, adding water 1 tablespoon at a time if the pan dries. Stir in the vinegar. Set aside; keep warm.

　　

Step 2

When the potatoes are tender, split them open, and top with the caramelized onions and shaved Parmesan. Serve warm.

　　Reprinted with permission from The Martha Stewart Living Cookbook: The New Classics by Martha Stewart Living Magazine, copyright © 2007. Published by Clarkson Potter, a division of The Crown Publishing Group.Buy the full book from Amazon.