Boil the Pasta: Bring a large pot of salted water to a rolling boil. Add penne pasta and cook for about 10 minutes until al dente, reserving ½ cup of the pasta water before draining.

Sauté the Garlic: In a skillet, melt 4 tablespoons of unsalted butter over medium heat. Add minced garlic and sauté for 1-2 minutes until fragrant, but do not brown.

Create the Roux: Sprinkle in 1 tablespoon of all-purpose flour, stirring constantly for 1 minute to form a roux.

Add the Milk and Cream: Gradually whisk in 1.75 cups of whole milk and 0.5 cups of heavy cream, bringing to a simmer for 3-5 minutes until thickened.

Incorporate the Parmesan: Reduce heat and stir in 1 cup of grated Parmesan until melted and smooth. Season with salt, black pepper, and red pepper flakes to taste.

Combine Pasta and Sauce: Mix drained penne into the sauce, adding reserved pasta water to adjust consistency if needed.

Garnish and Serve: Remove from heat and garnish with fresh parsley and extra Parmesan if desired. Serve immediately.