Preheat your oven to 350°F (175°C) and grease an 8-inch square baking dish.

Cook the elbow macaroni according to package directions until al dente (still slightly firm). Drain well and set aside.

In a large saucepan, melt ¼ cup butter over medium heat. Whisk in the flour, salt, pepper, mustard, and paprika to create a roux. Cook for 1-2 minutes, stirring constantly.

Gradually whisk in the milk, stirring constantly until the mixture is smooth. Continue cooking over medium heat, stirring frequently, until the sauce thickens slightly (about 5-7 minutes).

Remove from heat and stir in 1¾ cups of the cheddar cheese and all of the Gruyère or Monterey Jack until fully melted and smooth.

Add the cooked macaroni to the cheese sauce and stir until well coated.

Pour half of the mac and cheese mixture into the prepared baking dish. Sprinkle with half of the remaining cheddar cheese. Add the remaining mac and cheese and top with the rest of the cheddar.

In a small bowl, mix the breadcrumbs with 2 tablespoons of melted butter. Sprinkle this mixture evenly over the top of the macaroni.

Bake in the preheated oven for 25-30 minutes, or until the sauce is bubbly and the top is golden brown.

Allow to cool for 5 minutes before serving to let the sauce set slightly.