Bring a large pot of salted water to a boil and cook the macaroni until just tender. Drain and set aside.
In a medium saucepan, melt 2 tablespoons butter over medium heat. Whisk in the flour and cook for one minute to form a smooth paste.
Slowly pour in the milk while whisking. Continue cooking and stirring until the sauce thickens enough to coat the back of a spoon.
Remove the sauce from the heat. Stir in the shredded cheddar cheese, salt, and pepper until the cheese melts and the sauce turns smooth.
Add the drained macaroni to the cheese sauce and stir until every piece is coated.
Transfer the mixture to a greased baking dish. In a small bowl, combine the breadcrumbs with the melted tablespoon of butter, then sprinkle evenly over the top.
Bake at 375°F for 20 to 25 minutes until the topping turns golden and the edges bubble. Let it rest for a few minutes before serving.