Bring a large pot of salted water to a boil, add elbow macaroni, and cook for 7-8 minutes until al dente. Drain and reserve some pasta water.

In a medium saucepan over medium heat, melt 3 tablespoons of butter, then whisk in 3 tablespoons of flour for 1 minute until light golden.

Slowly add 2 cups of milk, whisking continuously for 3-4 minutes until thickened.

Remove from heat and stir in 2 cups of shredded cheddar cheese until melted and smooth.

Fold the cooked pasta into the cheese sauce, adding reserved pasta water if the sauce is too thick.

Preheat oven to 350°F (175°C). Transfer to a greased baking dish, combine breadcrumbs with melted butter, and sprinkle over the top. Bake for 20-25 minutes until golden.