How to Make It
Preheat the oven to 375°F.
While the pasta is cooking, in a medium saucepan, heat the oil over medium high heat until hot, then whisk in the flour and cook, whisking, until the flour is fragrant, about 4 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 cheeses until melted, then whisk in the broccoli. Season the sauce with salt and pepper to taste. Toss the pasta together with the sauce and transfer to a 3-quart baking dish.
Bake the mac and cheese until the filling is bubbling, 25 to 30 minutes. Serve.