Boil macaroni in salted water until tender, drain well.
Melt butter in a saucepan, whisk in flour for 1 minute to create a roux.
Gradually pour in milk, whisking continuously until sauce thickens.
Stir in cheddar cheese, salt, and pepper until melted and smooth.
Mix sauce with pasta, transfer to a baking dish, sprinkle breadcrumbs on top, and bake at 190°C for 15 minutes.