1 pounnd medium shell pasta
2 tablespoons butter
2 tablespoons flour
1 1/2 cups half-and-half or whole milk
1 cup chicken broth
2 tablespoons extra virgin olive oil (EVOO)
3 cloves garlic, grated or finely chopped
1 teaspoon anchovy paste (optional)
Bring a large pot of water to a boil, salt it, add the pasta and cook until al dente. Drain.
In a large saucepan, melt the butter over medium heat. Whisk in the flour and cook for 1 minute,then whisk in the half-and-half and chicken broth. Season the sauce with salt, pepper and the nutmeg and simmer, stirring occasionally, until thickened, 6-7 minutes.
In a large skillet, heat the EVOO, 2 turns of the pan, over medium heat. Add the garlic and anchovy paste, if using, and cook for 1 minute. Add the shrimp and radicchio, increase the heat and cook, stirring, until the shrimp is pink and the radicchio is tender, 3-4 minutes.
Pre-heat the broiler. Stir the Parmigiano Reggiano into the white sauce. Add the pasta, shrimp and radicchio and toss. Pour into a buttered casserole and sprinkle the asiago on top. Broil until the cheese is melted, about 3 minutes; serve hot.