Cook the elbow macaroni according to the package instructions until al dente.

Drain well and set aside.

In a quart-sized jar with a tightly-sealed lid, combine the milk, all-purpose flour, and onion powder.

Shake the jar vigorously for about 1 minute to create a smooth mixture.

In a large mixing bowl, combine the flour mixture, 3 1/2 cups of shredded sharp Cheddar cheese, and the cooked macaroni.

Stir until the macaroni is thoroughly coated with the cheese mixture.

Transfer the macaroni mixture into a lightly greased 13x9-inch baking dish or use 2 (11-inch) oval baking dishes if preferred.

Evenly sprinkle the soft breadcrumbs over the top of the macaroni mixture.

Then, sprinkle the remaining 1 cup of shredded sharp Cheddar cheese evenly over the breadcrumbs.

Drizzle the melted butter evenly over the cheese layer.

Preheat your oven to 350°F (175°C).

Bake the macaroni and cheese in the preheated oven for approximately 45 minutes, or until the top turns a beautiful golden brown and the cheese is bubbling.

Once it's done, garnish the macaroni and cheese with freshly ground black pepper to taste.

Enjoy your homemade Classic Macaroni and Cheese!