Bring a large pot of salted water to a rolling boil. Add elbow macaroni and cook according to package directions until al dente, usually about 7-9 minutes. Drain and set aside.

In a medium saucepan, melt 4 tablespoons of unsalted butter over medium heat. Stir in an equal amount of all-purpose flour to create a roux.

Gradually whisk in 2 cups of whole milk, whisking until it starts to thicken, about 5-7 minutes.

Remove from heat and stir in 1.5 cups of sharp cheddar cheese and 1 cup of Monterey Jack cheese until melted.

Gently fold in the macaroni, ensuring each piece is evenly coated.

Optional: Transfer to a greased baking dish and bake at 350°F for about 20 minutes for a bubbly top.