- 1 (16 ounce) package shell pasta
- 2 tablespoons olive oil
- 1 pound sliced cremini mushrooms
- 1 small red onion, diced
- salt and ground black pepper to taste
- 1 large head radicchio – halved, cored, and thinly sliced
- 4 cloves garlic, minced
- 2 tablespoons minced fresh sage
- 1/4 cup butter
- 1/4 cup all-purpose flour
- 2 cups milk
- 3 cups grated Asiago cheese
- 1 1/2 cups heavy whipping cream
- 1 1/2 cups freshly grated Parmigiano-Reggiano cheese, divided
- 1/2 teaspoon salt
- 1/4 teaspoon ground black pepper
- 1/2 cup panko bread crumbs
- Bring a large pot of lightly salted water to a boil. Cook shell pasta in the boiling water, stirring occasionally until still firm to the bite, about 9 minutes. Drain.
- Preheat oven to 350 degrees F (175 degrees C). Butter a 9×13-inch baking dish.
- Heat olive oil in a large pot over medium heat. Add mushrooms, onion, and salt and pepper to taste. Cook and stir until mushrooms have browned and onion is translucent, about 7 minutes. Add radicchio, garlic, and sage; cook until radicchio has wilted and garlic is fragrant, about 3 minutes. Remove from heat and stir in pasta.
- Melt butter in a saucepan over medium-high heat. Whisk in flour; cook until foaming. Pour in milk, whisking constantly, until mixture comes to a boil and thickens, about 5 minutes. Remove from heat; whisk in Asiago cheese, heavy cream, 1 cup Parmigiano-Reggiano cheese, 1/2 teaspoon salt, and 1/4 teaspoon black pepper until sauce is melted and smooth.
- Pour sauce over pasta mixture; stir until thoroughly combined. Transfer to prepared baking dish. Top with remaining 1/2 cup Parmigiano-Reggiano cheese and panko.
- Bake in the preheated oven until bubbly, about 30 minutes. Broil until topping is golden brown, about 1 minute.