01 -
Cook penne pasta according to package directions until al dente. Drain well and set aside.
02 -
While the pasta is cooking, melt butter in a large saucepan over medium heat. Add minced garlic and cook, stirring frequently, for 1 minute until fragrant but not browned.
03 -
Sprinkle the flour over the butter and garlic mixture. Cook, stirring constantly, for 1 minute to remove the raw flour taste and create a smooth paste (roux).
04 -
Gradually pour in the milk and chicken broth while whisking continuously to prevent lumps. Continue cooking and stirring constantly until the sauce comes to a gentle boil and thickens, about 5 minutes.
05 -
Stir in the grated Parmesan cheese, dried parsley, garlic salt, and pepper. Continue stirring until the cheese has completely melted and the sauce is smooth.
06 -
Add the cooked pasta to the sauce and stir gently to ensure all pasta is evenly coated. If using, add the mozzarella cheese and stir until melted and incorporated.
07 -
Serve immediately while hot. The sauce will continue to thicken as it cools.