Directions

• Preheat the oven to 400°F. In a large pot of boiling salted water, cook the pasta until al dente, then drain.
• While the pasta is cooking, in a large heavy pot, heat the oil over medium high heat until hot. Whisk in the flour and cook, whisking, until the flour is fragrant, about 3 minutes. Whisk in the milk and 1/2 teaspoon each salt and pepper, then bring to a boil, whisking. Boil until the milk is slightly thickened, about 8 minutes. Remove from the heat and whisk in the cheddar and Monterey Jack cheeses until melted, then whisk in the chicken. Season the sauce with salt and pepper to taste.
• Toss the pasta together with the sauce and transfer to a 3-quart baking dish. Sprinkle evenly with the parmesan cheese. Bake the casserole until the filling is bubbling and the cheese is browned on top, 20 to 25 minutes. Serve.