Cook the Bowtie Pasta:

Bring a large pot of water to a rolling boil and season generously with salt. Add the bowtie pasta and cook according to the package instructions until al dente. Before draining, reserve ½ cup of the pasta water, then set the pasta aside.

Prepare the Beef Mixture:

Heat olive oil in a large skillet over medium heat. Add the ground beef and cook, breaking it apart with a spatula, until it browns evenly, approximately 5-7 minutes. Stir in the chopped onion and minced garlic, cooking until the onion becomes translucent, about 3 minutes. Incorporate the Italian seasoning and red pepper flakes (if using), seasoning with salt and pepper to taste. Remove the cooked beef mixture from the skillet and set it aside.

Make the Garlic Butter Sauce:

Using the same skillet, melt the butter over medium heat. Add the minced garlic and sauté for about 1 minute, until fragrant. Sprinkle in the flour and whisk continuously for 1-2 minutes, creating a smooth roux. Gradually pour in the milk while whisking, ensuring a lump-free consistency. Allow the mixture to simmer gently until it thickens, approximately 3 minutes.

Combine Everything:

Reduce the heat to low and gradually mix in the shredded mozzarella and grated Parmesan, stirring until fully melted and smooth. Return the cooked pasta and beef mixture to the skillet, tossing to ensure even coating in the creamy sauce. If the sauce is too thick, incorporate small amounts of the reserved pasta water until the desired consistency is achieved.

Serve:

Portion the cheesy beef and bowtie pasta into serving bowls. Garnish with freshly chopped parsley and additional Parmesan, if desired. Serve warm and enjoy.