How to Make It
Preheat oven to 400˚F. Prepare macaroni according to package directions. Drain.
Melt 1/4 cup of the butter in a large skillet over low. Add flour; cook, whisking constantly, until smooth, about 1 minute. Increase heat to medium. Gradually whisk in milk; cook, whisking constantly, until thickened and bubbly, about 15 minutes. Whisk in salt and pepper.
Add pasta and 2 cups of the cheese to sauce, and toss to combine. Transfer to a lightly greased (with cooking spray) 3-quart baking dish; top with remaining 1 cup cheese. Cut remaining 2 tablespoons butter into pieces, and dot pasta mixture with butter.
Bake in preheated oven until lightly browned, 20 to 24 minutes.