Begin by preheating your oven to 375°F (190°C) and grease the baking dish with butter or use cooking spray.
Bring a large pot of water to a boil while adding salt. Cook the elbow macaroni according to the package instructions until al dente. Drain the pasta and set it aside.
Melt the butter in a medium saucepan over medium heat. Add the flour and whisk continuously to create a roux. Cook the roux for 2-3 minutes until it becomes a light golden color.
Incorporate the milk into the mixture slowly and continuously to prevent the formation of lumps. Continue stirring until the sauce thickens and reaches a smooth consistency.
Reduce the heat to low, and add the shredded cheddar, Gouda, and Parmesan cheeses to the sauce. Stir until all the cheeses have melted and the sauce is creamy and velvety.
Mix in the Dijon mustard, garlic powder, salt, and pepper. Adjust the seasonings to suit your taste.
Add the cooked macaroni to the cheese sauce, mixing until the pasta is evenly coated.
If desired, transfer the mac and cheese mixture to the greased baking dish and sprinkle breadcrumbs on top for a crunchy topping.
Bake in the preheated oven for 25-30 minutes or until the top is golden and bubbling.
Take it out of the oven and allow to cool slightly before serving.