Melt 2 tablespoons butter in a saucepan over medium heat
Add 2 tablespoons all-purpose flour
Whisk constantly for 1 to 2 minutes
Slowly add 2 cups milk while whisking
Cook and whisk until the sauce thickens
Add 1/2 teaspoon salt
Add 1/4 teaspoon black pepper
Add 1/4 teaspoon garlic powder, if desired
Add 1/4 cup grated Parmesan cheese, if desired
Stir until smooth
Toss with cooked pasta immediately