- 2 tablespoons unsalted butter, plus more for the dish
- 1 1/2 pounds sweet potatoes, peeled and cut into 1 1/2-inch pieces
- 1/3 cup extra-virgin olive oil
- 2 teaspoons thyme leaves
- Kosher salt
- Freshly ground pepper
- 1 pound torchio or rigatoni
- 2 1/2 cups milk
- 2 tablespoons all-purpose flour
- 1 cup shredded packed imported Fontina cheese (5 ounces)
- 1 pound Cantal cheese or other Swiss-style cheese—3/4 pound cut into 1-inch cubes, 1/4 pound shredded
- 3/4 cup packed freshly grated Parmigiano-Reggiano cheese
- Pinch of freshly grated nutmeg
- 1/2 cup heavy cream
- 1 large head of radicchio, sliced 1 inch thick
- 3/4 teaspoon minced rosemary
- 4 ounces pecans, chopped (3/4 cup)
- Slivered flat-leaf parsley, for garnish
- Preheat the oven to 400°. Lightly butter a 9-by-13-inch baking dish. On a baking sheet, toss the sweet potatoes with 1/4 cup of the olive oil, the thyme and 1 teaspoon of salt; season with pepper. Roast the potatoes for 20 minutes, stirring occasionally, until tender.
- Meanwhile, cook the pasta in a pot of salted boiling water until almost al dente, 5 minutes for torchio and 10 minutes for rigatoni. Drain, rinse under cold water and return to the pot.
- In a small saucepan, bring the milk just to a simmer. In a medium saucepan, melt the 2 tablespoons of butter. Add the flour and cook over moderately low heat, whisking frequently, until lightly golden, about 3 minutes. Whisk in the hot milk in 3 additions until incorporated. Cook over moderate heat, whisking often, until thickened, 10 to 15 minutes. Stir in the Fontina, the shredded Cantal, 1/4 cup of the Parmigiano and the nutmeg until the cheeses are melted. Stir in the heavy cream and season with salt and pepper. Stir the cheese sauce into the pasta.
- In a medium bowl, toss the radicchio with the rosemary, the remaining olive oil and 1/2 teaspoon of salt. Season with pepper and toss, then add to the pasta and mix well. Spread half of the pasta in the prepared baking dish. Tuck in half each of the sweet potatoes, cubed Cantal and pecans. Repeat with the remaining pasta, sweet potatoes, Cantal and pecans. Sprinkle the remaining 1/2 cup of Parmigiano on top.
- Cover the baking dish with foil and bake for 10 minutes. Uncover and bake for about 10 minutes longer, until the cheese is melted and the pasta is tender. Let the baked pasta stand for 15 minutes. Garnish with the slivered parsley and serve.
The unbaked pasta can be refrigerated overnight. Bring to room temperature before baking.
To balance the dish's heaviness, try a tangy Pinot Grigio or a lean, red-fruited wine from Sicily's Mount Etna.