Start to finish: 1 hour, 40 minutes (40 active)
Servings: 10 to 12
1 3/4 cups whole milk
2 cups heavy cream
4 large sprigs fresh thyme, crushed with a rolling pin
1 bay leaf
4 garlic cloves, smashed
2 1/4 teaspoons kosher salt
1/2 teaspoon freshly ground black pepper
1 pound russet potatoes
1 pound turnips
1/2 pound carrots
1/2 pound parsnips
2 ounces freshly grated Parmigiano-Reggiano
3/4 cup panko breadcrumbs
2 tablespoons extra-virgin olive oil
Preheat the oven to 375 degrees; adjust the oven rack to the middle position.
In a medium saucepan, combine the milk, cream, thyme, bay leaf, garlic, salt and pepper; heat the mixture over medium-high heat until bubbles form around the edge. Remove from the heat, cover, and let steep while you prepare the vegetables.
Peel all the root vegetables. Using a mandoline or the slicing disk of a food processor, slice them crosswise, 1/8-inch thick. Remove and discard the thyme, bay leaf and garlic cloves from the cream mixture and pour one-fourth of the mixture into a 9-by-13-inch baking pan. Add the vegetables and the remaining milk mixture to the baking pan (the liquid will just come up to the level of the vegetables). Stir the vegetables to make sure they are separated and then press them down to distribute them evenly. Bake the gratin on the middle shelf of the oven for 25 minutes. Remove the pan from the oven and press the vegetables down with a large metal spatula. Return the gratin to the oven and bake until the liquid has thickened and vegetables are tender when pricked with a knife, about 15 to 25 minutes more.
In a bowl combine the cheese, panko and oil; sprinkle the mixture evenly over the top of the pan. Return the pan to the oven and bake until the top is browned, about 10 minutes.
Cool for 5 minutes before serving.
Nutrition information per serving: 261 calories; 158 calories from fat; 18 g fat (10 g saturated; 0 g trans fats); 56 mg cholesterol; 552 mg sodium; 21 g carbohydrates; 3 g fiber; 6 g sugar; 6 g protein.
Sara Moulton, Associated Press