Start by bringing a large pot of salted water to a rolling boil over high heat. Add 2 cups of elbow macaroni and cook for about 8 minutes or until al dente. Drain and set aside in the pot.

In a medium saucepan, melt 4 tablespoons of butter over medium heat. Whisk in ¼ cup of all-purpose flour for about 2 minutes until a light golden roux forms. Gradually add 2 cups of whole milk, whisking continuously for about 5 minutes until thickened.

Reduce heat to low, add 1 cup of shredded sharp cheddar cheese and 1 cup of shredded Monterey Jack cheese to the sauce. Stir until melted and smooth.

Season the sauce with 1 teaspoon of salt, ½ teaspoon of black pepper, and ½ teaspoon of garlic powder. Adjust to taste.

Pour the cheese sauce over the cooked macaroni in the pot, stir thoroughly until every piece is coated.

If desired, fold in optional add-ins such as ½ cup of crispy bacon pieces or 1 cup of steamed broccoli.

Preheat your oven to 350°F (175°C). Transfer the mixture into a greased 9x13-inch baking dish and bake for 20-25 minutes until bubbly and golden brown.

Remove from the oven and let cool for about 5 minutes before serving.