Preheat your oven to 350°F (175°C). Grease a 2-quart baking dish and set aside.
Cook the elbow macaroni according to package instructions until al dente. Drain and set aside.
In a large saucepan, melt the unsalted butter over medium heat.
Once the butter is melted, whisk in the all-purpose flour to form a roux. Cook, whisking constantly, for 1-2 minutes, or until the roux is golden brown and fragrant.
Gradually pour in the whole milk, whisking constantly to prevent lumps from forming.
Continue to cook the sauce, whisking frequently, until it thickens enough to coat the back of a spoon, about 5-7 minutes.
Reduce the heat to low and stir in the shredded sharp cheddar cheese and shredded mozzarella cheese until melted and smooth.
Season the cheese sauce with garlic powder, onion powder, salt, and black pepper, to taste.
Add the cooked elbow macaroni to the cheese sauce and stir until well coated.
Transfer the macaroni and cheese mixture to the prepared baking dish, spreading it out evenly.
If desired, sprinkle breadcrumbs over the top of the macaroni and cheese for added crunch.
Bake the macaroni and cheese in the preheated oven for 20-25 minutes, or until bubbly and golden brown on top.
Remove from the oven and let it cool for a few minutes before serving.
Garnish with chopped fresh parsley, if desired, before serving.
